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No system of positive law can recognize any principle which would entitle a person to violate the law because on his view the law conflicted with some higher social value.[1]

Civil disobedience has an honourable history, and when the urgency and moral clarity cross a certain threshold, then I think that civil disobedience is quite understandable, and it has a role to play.[2]


Consider this: Next year, the Intergovernmental Panel on Climate Change (IPCC) releases a new assessment report. The report, reflecting the work of thousands of scientists from all over the world, confirms that humanity causes global warming. It also considers “virtually certain” the probability that business-as-usual trends in anthropogenic greenhouse-gas (GHG) emissions over the following two years will increase the average global temperature by at least 6 °C.[3] After two years, abrupt and irreversible changes in the global climate will become unavoidable over the medium or long term. Ecological processes will cross various thresholds, thereby triggering feedback loops, runaway global warming, and tip the planetary ecosystem into a new, fundamentally different state. On the publication of the report, civil unrest erupts in various countries. International leaders meet but fail to agree on a common action plan amid growing international tensions. In Canada, public demonstrations organized by environmental groups take place in major cities. A small number of organizations, dubbed “eco-terrorists” by the mainstream media, adopt civil-disobedience tactics to take direct action against GHG sources.[4] One of these groups decides to wage a campaign of vandalism to immobilize motor vehicles based on the fact that the transport sector is a major source of GHG.[5] The police arrest a number of activists suspected of systematically puncturing car tires, obstructing exhaust systems, and adding sugar to gasoline in fuel tanks. At trial, the activists raise the defence of necessity. The activists plead that concern about global warming is the only motive for their actions. Invoking the IPCC report, they argue that continued GHG emissions constitute an imminent peril to humanity’s survival, that immediate action against GHG emissions is an absolute imperative, and that the damage they caused is minute compared to the harm that they are attempting to avert. Should the court convict or acquit the activists?[6]

This apocalyptic scenario could be worthy of a science-fiction movie. It is also not far from the current reality of global warming, according to some reports.[7] In 2007, the IPCC Fourth Assessment Report examined a range of scenarios and concluded that they would lead to an increase in global mean temperatures between 1.6 ºC and 6.9 ºC by the end of the twenty-first century.[8] However, actual anthropogenic GHG emissions exceed even the highest IPCC forecasts.[9] More recent climate projections show that the IPCC’s scenarios are very optimistic; they establish a median probable surface warming of 5.3 ºC by 2100, with a 90 per cent confidence interval of 3.5 ºC to 7.4 ºC.[10] A rise of 5 ºC or more in the average global temperature could lead to a nightmare scenario, with possible consequences such as these:

Most of the tropics, sub-tropics and even lower mid-latitudes are too hot to be inhabitable. The sea level rise is now sufficiently rapid that coastal cities across the world are largely abandoned. Above 6[º]C, there would be a danger of “runaway warming”, perhaps spurred by release of oceanic methane hydrates. Could the surface of the Earth become like Venus, entirely uninhabitable? Human population would be drastically reduced.[11]

Some prominent scientists argue that disaster in the near future may already be unavoidable, with billions to starve and ecosystems to collapse.[12] The global system is already irreversibly headed for ocean warming and acidification, massive biodiversity reduction, destruction of local ecosystems, and increasingly frequent and severe extreme weather events.[13] Estimates suggest that global warming already causes 350,000 deaths per year, a figure that will rise to one million by 2030 if decisive action is not taken.[14] Plans prepared by armed forces posit that the catastrophic consequences of climate change will require “full scale stability operations.”[15] Yet governments around the world appear to have abandoned efforts to achieve an international treaty to curb GHG emissions.[16]

Whatever the anticipated effects of climate change, the question raised by the fictive scenario about the use of the defence of necessity is not purely hypothetical. On the contrary, it reflects issues that have already appeared before the courts. Firstly, civil-disobedience movements spurred by the perceived threat of irreversible tipping points and catastrophic environmental changes have already materialized in some countries.[17] Secondly, environmental activists engaged in civil-disobedience campaigns and faced with criminal charges have invoked the defence of necessity.

In England, three cases have recently attracted attention. In 2008, six Greenpeace activists who had attempted to shut down a coal-fired power station by climbing its chimney were cleared of criminal charges, as it was held that they were trying to prevent climate change from causing greater property damage.[18] In 2009, a court rejected the defence of necessity raised by twenty-two activists who hijacked a coal train to stop emissions from another power station in order to fend off imminent devastation due to global warming.[19] In 2010, an interlocutory judgement confirmed the availability of the defence of necessity to twenty activists charged for conspiracy to occupy and shut down yet another coal-fired power plant.[20]

Environmental activists in the United States have also pleaded the defence.[21] In 2009, an activist placed winning bids for oil and gas exploitation leases on federal lands at an auction in order to protest against global warming.[22] The activist faced criminal charges for interfering with the auction and making false statements on bidding forms.[23] The court rejected his defence based on necessity and sentenced him to two years in prison.[24] This case could be portrayed as a case of political imprisonment, since no adverse consequences resulted from the activist’s actions.[25]

The invocation of necessity by environmental activists is not theoretical in Canada either. The defence was raised in British Columbia by protesters who hindered logging operations in order to protect unique forest ecosystems and in Quebec by protesters who obstructed the opening of a plant that would emit highly carcinogenic organic pollutants.[26] Necessity is also relevant in the context of the national drive for greater fossil-fuel extraction despite public opposition and accumulating evidence of global warming due to GHG emissions. For example, citizen groups whose opposition to shale-gas exploration in Quebec has been ignored by the provincial government have announced that they may resort to hindering energy companies’ equipment to stop gas exploration in the St. Lawrence Valley.[27]

Beyond circumstantial justifications, a study of the defence of necessity in times of environmental crisis sheds light on more fundamental questions raised by the dialectical tension between certainty and flexibility within the legal order.[28] Certainty—or security, stability, consistency, predictability—and flexibility—or discretion—are two fundamental characteristics of legal frameworks.[29] On the one hand, certainty appears inherently tied to the law’s normative role.[30] In order to regulate conduct and order social interactions, the law must provide clear standards prospectively guiding the behaviour of those subject to it.[31] The pre-eminence of certainty and predictability may relate to law’s constitutive mechanisms. The law operates through general rules that are applicable to sets of situations. It relies on a process of abstraction that fits discrete and complex realities into pre-existing categories.[32] The law appears ill-equipped to deal with essentially unique events that cannot be reduced to standardized components and common patterns. However, including unforeseeable accidents, disasters without precedent, or unpredictable climatologic events within the ambit of the law via the defence of necessity allows for the normative processing of situations that are a priori ignored by legal regimes. In other words, the defence of necessity normalizes cases outside the law’s usual remit.[33] This extension of the law’s domain corresponds to an increase in legal stability.[34]

On the other hand, flexibility is essential to ensure that the law adapts to all possible situations and covers evolving social realities. Firstly, law does not provide absolute certainty. Legal decisions are never entirely predetermined; they rely on discretion.[35] The interpretation and application of rules inevitably involve substantive judgments that imply the particularized implementation of general norms on a case-by-case basis.[36] Secondly, legal regimes often have specific rules designed to deal with exceptional events on a prospective basis. Such mechanisms suspend the application of general norms in particular situations. For example, the doctrines of force majeure and frustration in contract law grant flexibility to legal interactions in unforeseen circumstances.[37] Similarly, necessity justifies a departure from penal norms in exceptional cases when adherence to the law would produce undesirable results. The defence of necessity thus increases the law’s flexibility by processing unique situations. However, if the exceptional becomes common, the application domain of mechanisms that deal with anomalous situations expands at the expense of legal frameworks applicable in normal circumstances. Necessity may encroach significantly on the normative structure that governs usual legal interactions if normality disappears as a result of climate change.[38]

In light of the foregoing, flexibility and certainty appear locked in a zero-sum game within the legal order, whereby the increased presence of one of these principles necessarily corresponds to a reduction of the other:

A significant part of the life of law has been attempts to balance the competing values of stability and flexibility. In some areas greater weight may be accorded to flexibility while in others stability is particularly valued. ...

... Despite lack of consensus as to its precise content and scope, the rule of law has been connected to notions of generality, clarity, certainty, predictability and stability of rules. At the same time, general legal rules must also be flexible enough to adapt to unforeseen circumstances and developments. When such developments take place over time there may be a sufficient lag to allow for changing the rules so as to accommodate the new realities. ... [T]he tension between the demands of stability and flexibility becomes almost unbearable when there is not enough time to adapt the laws to the changing circumstances and when immediate ‘specific’ action is deemed necessary.[39]

Hence the question introducing this article leads to an inquiry about the dialectical process between these two fundamental principles in the law. The law’s normative role requires minimal rigidity. Legal norms inevitably rely on abstract generalizations. Unique and unforeseeable events constitute an inherent challenge for the law. Specific mechanisms provide flexibility in exceptional cases. The application domain of these mechanisms may expand critically in times of crisis and emergency. The resulting increase in legal flexibility may threaten the law’s role as a framework of normative rules.[40]

In a context where the exceptional become commonplace, it is necessary to examine whether mechanisms that increase legal flexibility might diminish the certainty and stability of the law enough to damage its resilience. The aim of this article is to determine whether this risk is material with respect to necessity. Part I of the article provides a general presentation of the defence of necessity. Part II examines the definition of the defence in Canadian law and reviews cases where it has been raised in relation to environmental issues. Finally, Part III assesses the likelihood of successfully invoking necessity to defend illegal actions aimed at protecting the environment.

I. Contextualizing Necessity

This part provides a contextual overview of the origins and development of necessity. In its early philosophical articulation, necessity mediated between formal positivist legal frameworks and morality in exceptional circumstances (Part I.A). The defence’s later incarnation in international law shows that necessity is invoked by states committing wrongful acts to protect the environment, while scientific uncertainty generates irreducible ambiguity in the legal qualification of ecological perils (Part I.B). Finally, the more recent hesitations surrounding the reception of necessity in Canadian law also illustrate the law’s need for flexibility due to its inability to provide prospective guidance for all possible situations through general rules (Part I.C).

A. Philosophical Origins

A review of necessity’s underlying rationale immediately situates the defence at a breaking point of legal certainty and uncovers moral considerations behind the law’s positivist neutrality. Necessity relates to a situation in which an offence is committed to avoid a greater evil that would result from danger in exceptional circumstances.[41] Necessity dictates that “it is justifiable in an emergency to break the letter of the law if breaking the law will avoid a greater harm than obeying it” and that “it is excusable ... to break the law if compliance would impose an intolerable burden.”[42] Necessity thus aims at “avoidance of greater harm or the pursuit of some greater good” and recognizes “the difficulty of compliance with the law in emergencies.”[43] Succinctly stated, necessity condones the pursuit of the greater good rather than conformity with the letter of the law.[44]

Necessity’s role in increasing legal flexibility through departures from the law’s systematic application is readily apparent from the doctrine’s history. The defence’s intellectual roots can be traced to Greek antiquity. Aristotle indicated that a necessary action is involuntary because it is compelled by the circumstances and involves damages sustained to avoid greater harm.[45] During the Middle Ages, St. Thomas Aquinas commented on the observance of the law when an individual is faced with sudden peril needing instant remedy:

Since ... the lawgiver cannot have in view every single case, he shapes the law according to what happens more frequently, by directing his attention to the common good. Wherefore, if a case arise wherein the observance of that law would be hurtful to the general welfare, it should not be observed.[46]

These perspectives reveal characteristics that guide the doctrinal development of necessity in the law: the involuntariness of the action, the commission of a lesser harm to avoid a greater one, the law’s moral subjectivity, and the law’s inherent limitations when dealing with unique events. These cardinal ideas inform the reflection on necessity throughout the article.

B. International Advances

Following its earlier philosophical articulations, necessity materialized in international law during the seventeenth century, under the influence of Roman law. Grotius is credited with formalizing the doctrine as a right to self-preservation that could be invoked to justify actions otherwise “outside the pale of the law.”[47] Necessity evolved through interstate disputes to emerge as a distinct circumstance that precludes the wrongfulness of an act. It was formally articulated in the International Law Commission’s (ILC) draft articles on state responsibility.[48] First codified under article 33, and later under article 25, necessity can essentially be invoked if a state establishes that a series of cumulative conditions is satisfied.[49] Under the doctrine, a state can act in violation of its obligations if (i) it “is the only way for the State” (ii) “to safeguard an essential interest” (iii) “against a grave and imminent peril,” and (iv) the act will “not seriously impair an essential interest of [another state] ... or of the international community as a whole.”[50]

This definition prompts further considerations. Firstly, the condition that the course of action chosen by the state be the “only way” to safeguard its essential interest is ambiguous because necessity implies a choice between options. The act of the state is voluntary, distinguishing necessity from force majeure, which is defined as an irresistible force rendering compliance with the obligation materially impossible for the state.[51] Alternatives are always available, and a strict interpretation of this condition would negate the possibility of ever raising the defence successfully.[52] Secondly, both an “essential interest” and a “grave and imminent peril” may relate to environmental matters; thus a state may be able to violate international obligations to avert an impending ecological catastrophe.[53] However, environmental damage must be extremely urgent and sufficiently certain to be imminent, which entails much more than a risk or a possibility of harm.[54] A peril is considered imminent enough if it is remote in time but its realization is inevitable:

[A] “peril” appearing in the long term might be held to be “imminent” as soon as it is established, at the relevant point in time, that the realization of that peril, however far off it might be, is not thereby any less certain and inevitable.[55]

To illustrate this point with the example provided in the Introduction, the gradual nature of climate change does not preclude the invocation of necessity in international law insofar as the catastrophic consequences of global warming, however remote in time, are inevitable beyond a certain point. Nevertheless, the “grave and imminent peril” element requires a very high degree of certainty and constitutes a significant hurdle to ecological necessity in international law.[56] Scientific evidence is crucial to satisfy the condition of imminent peril,[57] yet environmental degradation is often progressive and difficult to demonstrate due to scientific debate and uncertainty.[58] This difficulty is amplified by the fact that ecological necessity is either about future events or events that did not happen as expected—arguably due to the very breach for which the defence is invoked.[59] Events that are certain to happen render a breach of obligations pointless. Uncertainty about the future is thus implicit in the concept of necessity. This certainty-uncertainty dialectic is especially evident in the case of ecological necessity due to the inconclusive nature of scientific evidence

C. Canadian Lineage

By comparison to its philosophical origins and its recognition in international law, the reception of the defence of necessity in Canadian law is relatively recent. The initial reticence towards the defence’s formal acceptance, which derives from legal developments in England, manifests the difficulty in applying the law to unique or unforeseeable events due to the law’s function as normative framework relying on general, prospective rules.[60] Although clearly defined by Blackstone in the latter half of the eighteenth century, the defence of necessity was later marginalized as a consequence of the English drive to codify criminal law during the nineteenth century.[61] The authors of the English Draft Code of 1879[62] decided against codifying the defence, arguing that some excuses and justifications against indictment should remain a priori undetermined because legal certainty stemming from exhaustive codification might otherwise entail undesirable condemnations in circumstances so unusual that they were impossible to foresee:

[W]e desire to state that in our opinion it is, if not absolutely impossible, at least not practicable, to foresee all the various combinations of circumstances which may happen, but which are of so unfrequent [sic] occurrence that they have not hitherto been the subject of judicial consideration, although they might constitute a justification or excuse, and to use language at once so precise and clear and comprehensive as to include all cases that ought to be included, and not to include any case that ought to be excluded.[63]

Thus the tension between the defence of necessity and prospective legal certainty is apparent in two primary ways: firstly, in the recognition that general legal norms cannot prescribe behaviour for all possible situations; and secondly, in the desire to render the law flexible by preserving judicial discretion with respect to exceptional or unforeseeable cases.

The initial basis for the English reticence toward the defence exerted a determining influence on Canadian law. The first Canadian criminal code, of 1892, was largely founded on the English Draft Code of 1879.[64] As a result, necessity was preserved as a residual and unarticulated common law defence to justify or excuse an otherwise illegal act.[65] As late as 1976, the Supreme Court of Canada remained hesitant to categorically recognize its existence following a review of case law and doctrine in American, Canadian, and English law:

On the authorities it is manifestly difficult to be categorical and state that there is a law of necessity, paramount over other laws, relieving obedience from the letter of the law. If it does exist it can go no further than to justify non-compliance in urgent situations of clear and imminent peril when compliance with the law is demonstrably impossible.[66]

This timid opening to a formal acceptance of the defence of necessity was solidified by subsequent case law that assumed the defence’s existence.[67] The Law Reform Commission of Canada further reinforced the drive to recognize the defence, in 1982, by recommending its codification.[68] In doing so, the commission nevertheless noted that necessity is a dangerous doctrine because it “allows personal assessment of conflicting evils and licenses individual choice between opposing values,” thus usurping the role of the legislatures and courts in resolving such conflict, and contradicting the legal framework of the criminal law that “imposes public standards ... [and] sets objective requirements.”[69] Necessity is “invoked equally by despots and rebels”[70] because it opens a space for moral judgements contesting the systematic application of the law. Hence the commission’s draft article made the defence available only to avoid harm to person or property to the explicit exclusion of harm of a political, economic, or social nature, in order to close the door on “claims to know better than society and its elected lawmakers.”[71] In line with the comments on the English Draft Code, the commission also reiterated that the codification of necessity would address problems caused by the incapacity to foresee—and so to specifically provide for by the law—the infinite variety of circumstances in which general, prospective rules may be applied. The doubts surrounding the defence were finally extinguished in 1984, when it was formally recognized by the Supreme Court of Canada in Perka.[72]

II. Increasing Legal Flexibility

In Part I, I attempted to bear out the features of necessity identified in the Introduction. Firstly, necessity may be raised in order to defend breaches of the law committed to protect the environment. Secondly, necessity increases flexibility in legal frameworks by providing a mechanism for dealing with unforeseen circumstances. Thirdly, necessity threatens the positive legal order by prioritizing individuals’ discrete value judgments in particular situations over the judgments of legislatures, courts, and society at large. In Part II, I examine the defence of necessity as defined in Canadian law and, in particular, as applied to environmental matters, in order to determine whether the general features of necessity outlined above are relevant in the Canadian context.

A. The Definition of Necessity

Justice Dickson, writing for the majority of the Supreme Court in Perka, formally recognized necessity as a “residual” common law defence in Canada, but he emphasized that it must be strictly controlled and scrupulously limited because it would otherwise threaten to engulf large portions of the criminal law.[73] Relying on the rationale that involuntary conduct cannot be deterred and that punishment of involuntary actions is pointless, the Supreme Court restricted the defence—as it did in Morgentaler—to “urgent situations of clear and imminent peril when compliance with the law is demonstrably impossible.”[74] To identify such situations where the “choice” to break the law is in fact a compulsion borne from “moral or normative involuntariness”, the Court established three cumulative tests that determine whether a wrongful act can be excused by necessity.[75]

The first test requires the existence of a peril, danger, or harm that must be imminent, or unavoidable and near. This test establishes whether the action taken by the person invoking necessity was indeed unavoidable. The peril must be such that normal human instincts cry out for action and make counsels of patience unreasonable.[76] The peril is imminent if it is “on the verge of transpiring and virtually certain to occur” rather than only foreseeable or likely.[77] However, when the danger clearly should have been foreseen and avoided, the accused cannot reasonably claim the existence of an immediate peril.[78] To determine whether the peril is imminent, the courts use a modified objective standard whereby “[t]he accused person must, at the time of the act, honestly believe, on reasonable grounds, that he faces a situation of imminent peril.”[79]

Inferences can be drawn from the indications given by the Supreme Court about the first test and, in particular, about the foreseeable and avoidable character of a peril. The foreseeable character of an imminent peril is essential for the emergence of a situation of necessity. The Court stated that the danger must be virtually certain; that is to say, it must be more than foreseeable. Moreover, the use of the modified objective standard (containing a subjective component) implies that the peril must be perceived by the accused before he or she breaks the law. Therefore, a peril that motivates illegal actions that are subsequently excused by necessity is always foreseeable from the accused’s perspective. As a result, when the Court mentioned that necessity cannot be raised when a peril is foreseeable and avoidable, it is actually only the avoidable character of the peril that can preclude the defence of necessity. At the same time, if a peril is foreseeable and unavoidable, any action to elude it becomes pointless, including illegal acts. The peril must be avoidable to some extent, and the accused must have some form of power to affect events leading to the peril.[80]

It follows that necessity requires perils to be avoidable, but some avoidable perils are not compatible with the defence. The main issue is to identify and delineate the ensemble of avoidable perils where necessity may be successful. Perils avoidable purely through legal means are not relevant. Only perils that may be avoided either by legal as well as illegal means or else solely through illegal means must be examined. With respect to the former, courts obviously cannot condone illegal acts committed to evade impending danger if the accused a priori had the choice of either a legal or illegal course of action to avoid the peril. By holding that necessity cannot succeed if the peril clearly should have been foreseen and avoided, the Supreme Court therefore implied that, in a situation where the defence can succeed, the accused has no significant capacity to perform legal acts to avert the danger, but he retains the capacity to perform illegal acts that may do so. These inferences from the Court’s statements about the first test directly lead to the second test.

The second test requires the absence of a reasonable legal alternative to the course of action undertaken. The question to ask is whether the accused could realistically have acted to avoid the peril without breaking the law, or more succinctly, whether there was a legal way out.[81] If there was a reasonable alternative to breaking the law, there is no necessity. The Supreme Court added that this test involves a realistic appreciation of the alternatives open to a person, indicating that “the accused need not be placed in the last resort imaginable” such that the act committed does not necessarily have to be the only possible response to the situation.[82] The modified objective standard also applies to the second test so that “[t]he accused person must, at the time of the act, honestly believe, on reasonable grounds, that he faces a situation of imminent peril that leaves no reasonable legal alternative open.”[83]

The third test requires proportionality between the harm inflicted and the harm avoided. In Perka, the Supreme Court stated that no rational criminal justice system could excuse the infliction of a greater harm to avert a lesser evil, and therefore, in such circumstances, the individual is expected to bear the lesser harm and refrain from acting illegally.[84] However, the Court specified in Latimer that

most situations fall into a grey area that requires a difficult balancing of harms. In this regard, it should be noted that the requirement is not that one harm (the harm avoided) must always clearly outweigh the other (the harm inflicted). Rather, the two harms must, at a minimum, be of a comparable gravity. That is, the harm avoided must be either comparable to, or clearly greater than, the harm inflicted. ...


The evaluation of the seriousness of the harms must be objective. A subjective evaluation of the competing harms would, by definition, look at the matter from the perspective of the accused person who seeks to avoid harm, usually to himself. The proper perspective, however, is an objective one, since evaluating the gravity of the act is a matter of community standards.[85]

The three tests defined by the Court can elicit some reservations. As shown above, the first two tests are tautologically interdependent since the conditions required to meet the first test inevitably imply that the second test is passed, and vice versa. In fact, both tests, imminent peril and the absence of a reasonable legal alternative, demand that the illegal act be unavoidable.[86] As a result, the first two tests can hardly be differentiated and have limited usefulness because they do not add independent criteria to the general requirement that compliance with the law be demonstrably impossible.

Secondly, some aspects of the proportionality test are questionable. The consideration of alternate harms connotes a choice between interests or values that cohabits uneasily with the requirement of normative involuntariness.[87] Moreover, the defence is not confined to situations where the harm caused by the illegal act is less than the harm that would have resulted from compliance with the law. Notably, it also extends to situations where the harms caused and avoided are comparable. Hence a person placed in a situation of necessity has some latitude to favour a personal conception of the greater good over the values expressed through general legislative rules.

In addition, the proportionality test fails to impose a requirement that the harm caused be minimized. If many different illegal actions offer potential responses to a situation of necessity, the person breaking the law can decide to act in the most harmful way as long as the harm caused is comparable to or less than the harm avoided. To a certain extent, the person breaking the law may choose to act in a manner that maximizes personal benefit or reduces personal harm to the detriment of other interests. This risk would be avoided if the person breaking the law had to minimize the harm caused. Such a requirement is not foreign to the law. For example, the requirement to minimize the harm caused in situations akin to necessity is codified in an exception to a statutory prohibition on the disposal of substances altering the environment in Canadian waters.[88] The exceptional disposal must be “carried out in a manner that minimizes, as far as possible, danger to human life and damage to the marine environment.”[89]

Finally, the balancing of harms required by the proportionality test imbues the law with subjectivity by allowing the courts to second-guess the legislature and assess the relative merits of social policies underlying legislative prohibitions in the particular cases brought before them. In Perka, Justice Dickson stated that a defence of necessity relying on a utilitarian balancing between the benefits of obeying the law and the advantages of disobeying it would grant to the courts a role unfit for the judicial function, but he nevertheless proceeded to integrate the proportionality test into the defence.[90] Hence it can be argued that necessity allows violation of the law when courts exercise their moral judgement to the effect that the illegal action reflects society’s values.[91]

In fact, this last reservation about necessity challenges the conceptual foundations of the defence, whether it is defined as an excuse or as a justification.[92] The majority of the Supreme Court in Perka decided to categorize necessity as an excuse rather than a justification in order to prevent the courts from making moral judgements about an illegal act.[93] According to the Court, if necessity was a justification, tribunals would have the capacity to decide that an illegal act is not wrongful, implying that non-conformity with the law would be right in certain situations. Necessity, conceived as a justification, was rejected because tribunals must not make choices between evils by exculpating persons who disobey statutory norms on the basis that contravention of the law is more useful or beneficial according to some higher social value.[94]

Yet the proportionality test functions exactly in this way since prevention of an evil greater than or comparable to that resulting from the violation of the law is absolved of criminal liability.[95] Justice Wilson’s dissenting opinion in Perka emphasized that the maximization of social benefits implied in the utilitarian balancing of harms is a goal of legislative policy that does not properly belong to the judicial function.[96] Moreover, this balancing confuses the purpose of individual sentencing with standards of criminal liability, which must remain general.[97] The majority of the Court countered that categorizing necessity as an excuse preserves the objectivity of criminal law; necessary acts remain wrongful, but they are excusable in certain circumstances.[98] However, Justice Wilson pointed out that the normative involuntariness of a necessary action is assessed in the particular context of the accused’s personal situation, thus undermining the principle of the “universality of rights”, which requires “that all individuals whose actions are subjected to legal evaluation must be considered equal in standing.”[99]

In summary, whether characterized as an excuse or a justification, necessity might reduce the criminal law’s normative objectivity and increase legal flexibility in situations of imminent peril.[100] Necessity may also have the same effect with respect to the application of legal frameworks for the management of environmental crises and civil emergencies, since the defence can be raised against statutory or regulatory violations.[101] In particular, the proportionality test

would seem to favour greater availability of the defence of necessity for violations of regulatory offences than for criminal offences. Since by definition public welfare offences are generally less serious than true crimes—both in the sense of being less clearly wrong morally, and in terms of the foreseeability of harm from committing an offence—there may more often be circumstances in which the harm to society resulting from excusing a breach of a regulation would be less than the harm the offender or others would suffer from compliance with the letter of the law.[102]

Doctrinal sources also suggest that a reduction in the normativity of the law due to the availability of the defence might hamper the application of legal frameworks for environmental protection.[103] More specifically, it is argued that the defence could weaken the environmental obligations of polluters because the proportionality test favours the avoidance of harms to persons and property that usually appear more definite and substantial than damage to the environment.[104]

B. The Application of Necessity

A review of case law in matters related to environmental protection and natural resources management confirms the impact of the defence of necessity. Although instances where the defence is successful are rare, these cases demonstrate that necessity increases legal flexibility in the application of statutory norms.[105] In Boucher, the accused cut a tree on her immovable property without the authorization required under municipal regulations.[106] The accused admitted to the offence, but she invoked necessity to excuse her actions in the circumstances. Specifically, given that a tree branch had fallen in front of her house, other branches were resting on the roof of the house, and the tree was heard creaking, she argued that the security of the her children was threatened. The court accepted the defence on the basis that the tree posed an imminent danger on account of the accused’s situation, that the tree was cut on a Saturday when the municipality’s offices were closed, and that damage to the accused’s property as well as the threat to the security of her children outweighed any damage done to a tree. The court reached this conclusion despite the fact that the accused could have called the municipality at an emergency telephone number to obtain authorization to cut the tree without delay, could have pruned only the branches resting on the roof until authorization was obtained, and could have removed her children from the premises as her family did not yet reside at the house but would move in at a later date. In a similar decision rendered a year later by the same judge in Nehme, the defence was successful against charges of cutting four trees without municipal authorization, an action that was taken by the accused after a branch fell from one of the trees on the fence enclosing the accused’s immovable property.[107]

In Skinner, the accused faced charges of fishing at sea in a prohibited area and refusing to allow boarding of the fishing vessel by a fisheries officer in contravention of the Fisheries Act.[108] The charge of fishing in a prohibited area was dismissed on the grounds that the accused’s activities were not covered by the definition of “fishing”. The defence of necessity was successfully invoked in relation to the charge of obstructing the fisheries officer. The accused argued that the vessel could not stop because the nets were in tow and would have tangled with the propellers, thus threatening the vessel’s integrity. The trial judge considered that entanglement of the nets in the propellers was a peril sufficient to accept the defence of necessity. However, a number of facts render the court’s finding problematic. To begin with, the nets had been left in the water because the volume of fish caught exceeded the vessel’s storage capacity. The accused should also have expected a request to stop from an inspection officer since this had already occurred on the same morning. Furthermore, cutting the nets adrift would arguably have allowed the vessel to comply with the orders.

In Saint-Cajetan D’Armagh, a municipality dredged a river without conducting the environmental impact assessment and obtaining the authorization certificate required under the Environment Quality Act (EQA).[109] The river was dredged in 1986 to clear the bed of debris from a dike that broke in 1979 and caused yearly flooding in the spring. Various discussions between the municipality’s mayor and governmental authorities from 1980 to 1986 failed to provide a definitive solution to the problem. However, significant damage to riparian properties caused by serious flooding in the spring of 1986 impelled the municipality to address the issue in order to avoid similar flooding in 1987. The court found that the municipality was faced with an emergency and had to act to avoid further damage to property in riparian areas. It also took into account public officials’ duties to ensure public security and adequate watercourse maintenance. The court concluded that government authorities failed to act with diligence and thereby placed the municipality in an urgent situation that required action. This finding was made in spite of the fact that the municipality did not submit an application to obtain the authorization required under the EQA between 1979 and 1986 when flooding was a yearly occurrence, known and foreseeable to both the municipality and the riparian residents.

Western Forest Industries involved charges of emitting deleterious substances in a fish habitat in contravention of the Fisheries Act.[110] A dam reservoir was dredged annually, and its residue was usually dumped in the river downstream from the dam. In the events giving rise to the charges, however, a new dredging procedure had been implemented under the direct supervision of a fisheries officer: the dredged material was loaded onto trucks and disposed of at another location in order to protect fish habitats downstream. The discharge of deleterious substances occurred when a dump truck positioned precariously on the bank of the river had to have its contents off-loaded to prevent it from plunging into the river along with its driver. The court accepted that the discharge was necessary to preserve the security and health of the truck driver, but it mentioned that an experienced driver would not have attempted the manoeuver that led to the discharge.[111]

Finally, in Pootlass, the accused were charged with fishing at sea a few hours after close time in violation of the Fisheries Act.[112] The court accepted the defence of necessity on the basis that the accused worked to the point of fatigue in order to retrieve their nets but were unable to do so in time, owing to inclement weather. The court recognized that the accused could have cut their nets adrift to avoid committing the offence, but it found that the general close time was set arbitrarily with respect to the particular circumstances of the accused. The court added that there was no general harm from the breach of the close time since retrieval of the fish and nets was considered to be in the public interest and did not derogate from the provision’s primary purpose of preventing overfishing.

In summary, a study of the principles and criteria defining necessity in Canadian law suggests that the defence increases flexibility in the enforcement of statutory regimes for environmental protection and natural resources management. Cases where the defence has been used successfully point to an inventive reading of elements of the defence of necessity. Firstly, options other than breaking the law seem available in all cases other than when the life or health of an individual is threatened.[113] Secondly, the situations of necessity are foreseeable and easily avoidable—or at least not imminently urgent—in many cases.[114] Thirdly, the harms avoided are generally of an economic nature.[115] Fourthly, the defence prompts judicial assessments of the values and rationales underpinning legislative provisions in light of the facts brought before the courts.[116] Given these conclusions, it appears that necessity tends to be successfully invoked beyond the strict boundaries of its scope as defined by the Supreme Court. This, in turn, reduces the law’s normative power more than one would expect on a narrower application of the doctrine.

III. Dissolving the Law’s Normativity

The remaining issue is to determine whether the reduction in legal normativity as a result of the application of necessity critically affects the law’s functioning as a prescriptive framework for social interactions in the context of an environmental crisis or emergency. Part III thus examines the factors that may increase the impact of necessity during such crises or emergencies. It also assesses the likelihood of environmental activists successfully raising the defence.

A. Necessity and Environmental Crisis

Three factors may render the law flexible to such an extent that positive norms could lose their prescriptive value for all practical purposes in a situation of environmental emergency or crisis. Firstly, the increased unpredictability of climatic variations could multiply the occasions in which the defence may be invoked to excuse violations of statutory regimes. For example, extreme rainfall is expected to become more violent and frequent than in the past, leading to the emergence of new flood patterns as well as higher risks of flooding damage.[117] For populations located in flood areas, unprecedented measures at odds with existing laws may be required in order to cope with unforeseen dangers and risks to security or life. In other words, the heightened prevalence of extreme weather events such as floods, ice storms, and hurricanes may increase the likelihood that individuals or communities will face imminent perils, resulting in more instances where the defence of necessity could be invoked.

Secondly, the defence may be applied more widely, owing to a tendency toward greater regulation of civil emergencies and crises. For example, following recommendations from two governmental commissions investigating the 1996 Saguenay floods and the 1998 ice storm, the Civil Protection Act (CPA) was adopted in 2001 in Quebec to provide a management framework for extreme weather events and civil emergencies.[118] The purpose of the CPA is protection “against disasters, through mitigation measures, emergency response planning, response operations ... and recovery operations” when “an event caused by a natural phenomenon, a technological failure or an accident, whether or not resulting from human intervention ... causes serious harm to persons or substantial damage to property and requires unusual action on the part of the affected community.”[119] Under the CPA, the occurrence of a disaster can trigger local or national states of emergency under which government authorities acquire the power to make requisition orders directing the conduct of citizens.[120] The CPA creates offences in order to penalize persons who do not follow emergency plans or orders.[121] New statutory provisions backed by penal sanctions, such as those found in the CPA, apply to previously unregulated perilous situations where necessity is particularly relevant, creating more possibilities for the invocation of the defence.

Thirdly and most importantly, necessity may successfully be invoked to defend those who commit illegal acts of civil disobedience to protect the environment in the context of extreme climate events. The fact that necessity could excuse political acts directed against the social order that the law is meant to protect is particularly significant because it could indicate a threshold in the continuum between legal certainty and flexibility. Beyond that threshold, the law may become incapable of performing its function and ensuring its own normative power.

B. Necessity and Environmental Activism

The notion that necessity may successfully be used to defend those who commit illegal acts of civil disobedience to protect the environment is based on two considerations. Firstly, the defence has already been successful in a case where the law was broken for the purpose of protecting the environment. In St-Séverin, a municipality committed an offence when it installed waterworks and sewers without the ministerial authorization required under the EQA.[122] The court found that the authorization process was delayed by the obstruction of a civil servant and accepted the defence of necessity on the basis that the municipality’s aim was to stop contaminant discharges into the aquatic environment in conformity with the primary purpose of the EQA.[123]

In the court’s view, the imminent peril arose from the urgency of completing the sewer works before winter because of the sensitivity of the particular aquatic environment, the impossibility of performing the work in cold temperatures, as well as a possible increase in costs and the potential loss of a significant portion of government funding if the works were delayed for a year. The urgency of the situation was compounded, in the opinion of the court, by unexpected delays in the authorization process and the need to extend the work over a longer period to avoid shutting all municipal roads at the same time. The court did not undertake a detailed analysis of whether there was an absence of a legal alternative, even though a mandatory injunction could have been filed to request that the administrative authority use its discretionary power to grant or refuse an authorization for the works. However, the judgment is clear on the municipality meeting the proportionality requirement. Indeed, the court found that the works caused no damage to the environment because they complied with the standards and specifications provided by the legislative framework for environmental protection established under the EQA.[124]

There is a second consideration that points to the possibility of environmental activists successfully invoking necessity for acts of civil disobedience: such acts, especially in situations of environmental emergency, can objectively correspond to the requirements of necessity defined by the Supreme Court.[125] For example, necessity could be invoked in the hypothetical climate change–crisis scenario described in the Introduction: catastrophic peril is imminent; reasonable alternatives do not exist in the current political context, given that past efforts have failed to curb global warming and that the Canadian government opposes attempts to constrain GES emissions; and the balance of harms favours the destruction of road vehicles to avoid the collapse of the earth’s ecosystem and the suffering of billions.

However, an adequate correspondence between the requirements of the defence and specific factual situations of civil disobedience does not guarantee that courts would exculpate so-called eco-terrorists. The defence’s success in St-Séverin, despite the absence of imminent peril and the presence of legal alternatives, is likely due in part to the fact that the accused was a municipal authority conducting public interest works in a manner corresponding to the court’s conception of the greater good. The issue becomes more delicate when private citizens engage in civil disobedience and necessity is raised to defend illegal actions undertaken to protect the environment against legally authorized destructive activities that ultimately cause ecocide but that are socially accepted because they create jobs and generate prosperity for shareholders in the short term.[126]

Canadian courts have traditionally been averse to arguments related to civil disobedience and generally consider that civic-minded citizens trying to bring about social change by disobeying the law must be sanctioned, however commendable their goals and peaceful their actions may be.[127] The case law indicates that civil disobedience is not recognized as a defence at law but that necessity may be invoked to excuse acts of civil disobedience.[128] Although the possibility of successfully raising the defence in cases of civil disobedience by environmental activists exists in principle, the actual acceptance of necessity by courts as a defence for illegal acts motivated by political aims faces significant hurdles.

A review of the case law shows no instance where the defence of necessity has been successful in matters related to environmental activism in Canada. Furthermore, in one case, a court placed an additional restriction on the application of the defence. In MacMillan Bloedel, environmental activists protesting logging activities on Vancouver Island disobeyed a court order restraining them from continuing to hinder logging operations.[129] The activists invoked necessity because they believed that their actions would “break the chain of ecological destruction that would eventually ravage and destroy the planet.”[130] Following Perka, the British Columbia Court of Appeal found that necessity was not available because the accused had a reasonable legal alternative since they could have applied to have the order set aside by the courts. However, the judge added: “I do not believe the defence of necessity can ever operate to avoid a peril that is lawfully authorized by the law.”[131] The court therefore decided that necessity could not excuse illegal acts committed against the logging company because the company had an existing legal right to log the areas in question.

The basis for this additional restriction on the defence of necessity is debatable. It appears to be at odds with the Supreme Court’s reasoning in Perka, which directs the entire focus of judicial analysis to the involuntary nature of the necessary act to the exclusion of the legal context in which it is committed.[132] Moreover, the additional restriction may preclude invocation of the defence in cases where the defence should be successful. One can imagine a situation where the operation of an industrial process authorized under a number of statutory regimes, including environmental legislation, poses a sudden and lethal threat to a human life following an accidental malfunction or mistake, and the only way to prevent a tragedy is to halt the industrial process by causing some damage to the machinery. Here the additional requirement imposed by the court in MacMillan Bloedel would render necessity unavailable against charges of mischief in a situation falling squarely within the defence’s intended scope of application. The requirement would even invalidate the defence in cases where it has been accepted by the courts. In Skinner, the perilous situation was entirely covered by a statutory regime. Each of the three elements generating the peril independently or in conjunction was positively authorized by the law, including the casting of nets, the operation of a fishing vessel, and the fisheries officer’s power to make an order to stop fishing vessels.[133] According to the principle established in MacMillan Bloedel, necessity would not be available to defend the refusal to stop the vessel, because the peril was authorized by the law. In this context, the additional requirement imposed by the court in MacMillan Bloedel for a successful defence may not be considered a substantial obstacle to the application of the defence in cases of civil disobedience.

A more significant difficulty concerning the use of necessity by environmental activists is the notion that the democratic process is a form of legal alternative that can serve to alter policies, laws, and administrative decisions detrimental to the environment.[134] An essential premise behind this idea is that Canadian democracy grants all citizens the capacity to influence political decisions and administrative processes in meaningful ways, thereby precluding the materialization of a situation of emergency where there is no legal way out.[135] The courts recognize that democratic policy-making may sometimes exclude public participation, that the democratic process requires compromises, and that no single view can prevail unadulterated in the political arena.[136] Yet the failure of a group to persuade others of the rightness of its cause or to impose particular governmental or administrative decisions in specific cases implies the success of another equally valid viewpoint. Democracy preserves the rights of minorities to refine their unsuccessful political proposals and to try again to gather the support of a majority, adhesion, or conformity through various channels at different levels.

Setting up these arguments in opposition to civil disobedience implies that the Canadian democratic system is preferable to any other political system, is truly responsive to all inputs, and that participants in the democratic process make thoughtful decisions based on rational considerations.[137] Ultimately, this conception of democracy has an important procedural aspect that relies heavily on the rule of law as its central principle. In Drainville, Justice Fournier, quoting a speech given by one of his colleagues, linked the rule of law and civil disobedience as follows:

It is one of the fundamental principles of our democratic society that no one is above the law, and everyone is equal before the law. The rule of law is based on the fact that our current laws represent the will of the majority of the people. If a law no longer represents the will of the majority, then it should be changed but until it is changed by lawful means, it must be obeyed. Defiance of the law is not the answer.

He then went on in his own words:

Is “civil disobedience” or even “passive resistance” such a small infraction, or such a minimal use of force, that the “actus reus” ought to be overlooked? Should such activity as obstructing a road be justified by some sort of approval by the courts on the grounds that the motives are good and noble, or that the situation is really a “political” one? In light of the existing circumstances of this case, where it seems a just and appropriate political solution appears to have been found, this might be a tempting proposition. But certainly that would be tantamount to a declaration that, in some instances, at the discretion of some judge, and irrespective of the “rule of law,” there are times when “the ends justify the means.” Even in this case, where it appears that the government of Ontario may be about to change its policies and perhaps admit to a previous error in judgment, where it appears that a memorandum of agreement termed a viable “political solution” is now in place and that those protesters may have been morally right, surely, the process of legitimizing previously unlawful acts after the fact is an inherently dangerous concept which is simply not acceptable as an alternative to the “rule of law.”[138]

Civil disobedience thus identifies the point in the interplay between legal certainty and flexibility beyond which any compromise in the strict adherence to the rule of law is unacceptable. However, strict adherence to the rule of law also imposes the objective and correct application of the requirements of necessity defined by the Supreme Court, even if this results in excusing acts of civil disobedience.[139] The use of necessity to defend illegal acts that have a political dimension and are committed to avoid an imminent peril cannot be systematically rejected irrespective of their particular factual context simply because of the general availability of political alternatives in a democracy.[140] In a situation where a political or administrative decision taken in accordance with the law creates or provokes an imminent peril that corresponds to the criteria established by the Supreme Court, the courts will be called on to objectively assess whether the individual who broke the law to avert the peril had a reasonable opportunity of achieving the same result through legal means, including participation in a decision-making process such as public consultation or voting.[141] If an act of civil disobedience is contrary to the law but avoids a greater harm in the face of an imminent peril, the act must be excused in the absence of reasonable legal alternatives.

The case law provides examples of political alternatives pursued by groups engaged in civil disobedience in instances where necessity is raised.[142] Lanthier is particularly relevant as it concerns environmental activism. In that case, environmental activists were charged with obstructing peace officers during a protest to prevent the opening of a magnesium production plant that would discharge organochloride compounds into the environment, and at trial, they invoked necessity as a defence.[143] Prior to the protest where the illegal acts took place, the activists had attempted to block the plant through a variety of means, including public information meetings, peaceful demonstrations, and meetings with representatives of the company and the provincial government.[144] Despite the activists’ attempts to dissuade the government, a decree was issued authorizing the construction and operation of the production plant. The administrative process had been rushed so that the authorization would be granted before an international treaty banning organochlorides was signed by Canada.[145] Furthermore, the decree was issued before background assessments designed to inform the government’s decision were finalized. Moreover, the conditions and specifications imposed by the decree for the regulation of the plant’s release of organochlorides ignored official recommendations from a consulting government body that had urged caution.

Because injunctive recourses were too onerous for them, the activists decided to organize a protest as a measure of last resort in order to obstruct the workers’ access to the plant on the day of its opening. The activists considered the protest a success since it drew heavy media coverage and was relatively peaceful. However, a few protesters resisted arrest by the police and faced obstruction charges. Necessity was invoked to excuse the illegal acts committed to avoid the acute danger to human life and health generated by the release of organochlorides. The court rejected the defence on the basis that, since the act of resisting arrest does not address a peril, the accused obviously had the alternative not to break the law.[146] The court mentioned that its findings might have been different if the offence had been related to the hindering of the plant’s operations.[147] In such a case, in the court’s view, a reasonable doubt might have been raised as to commission of the offence, at least in respect of the imminent peril and proportionality requirements of the defence.[148] Indeed, the court appeared convinced that organochlorides are acutely toxic to humans and the environment, describing in detail the international scientific consensus recommending a zero-tolerance policy toward them.[149] However, the court gave no clue as to what its finding would have been on the “absence of legal alternatives” requirement in a factual context in which the activists had exhausted all options to influence the government’s decision.

In summary, necessity may excuse illegal acts committed by environmental activists if the situation corresponds to the applicable requirements, although such a defence would face significant hurdles. Despite these hurdles, necessity as defined in Canadian law may be easier to invoke for this purpose than in other jurisdictions where the requirements of the defence are more stringent. For instance, many jurisdictions have a causality requirement, whereby necessity is available only if the accused’s illegal action could reasonably be expected to avert the harm.[150] The absence of such a requirement in Canada significantly lightens the accused’s burden, especially in environmental matters, where connections between causes and effects are often difficult to prove because of long time lapses and the myriad variables affecting environmental processes.[151] In a jurisdiction where the additional requirement of causality exists, it may be almost impossible to raise necessity to defend the actions described in the example in the Introduction because such acts cannot be expected to negate the harm of global warming from GHG emissions from innumerable sources on a planetary scale. In Canada, the defence simply demands that the accused place evidence sufficient to raise the issue that the situation created by external forces was so emergent that failure to act could endanger life or health and that compliance with the law was impossible upon a reasonable view of the facts.[152] Given that there is no onus of proof on the accused, and given the application of the modified objective standard of proof, the relation between scientific causality and imminence may be considered a minor issue that does not warrant much attention in Canada, contrary to the international law context.[153]


Necessity knows no law. This proverb encapsulates the fundamental tension between legal frameworks that seek to normalize social behaviour and urgent action in response to unpredictable events. The defence of necessity provides a mechanism to accommodate this tension and fosters the law’s adaptation to unforeseen circumstances. In this article, necessity has served as the fulcrum for a reflection on legal flexibility and resilience in the context of climate change and environmental crisis.

A study of the conceptual foundations and requirements of the defence indicates that necessity increases the discretion of judges to make subjective assessments in the application of the law. Case law also shows that necessity augments legal flexibility. In cases involving charges related to environmental protection and natural resource management, courts have applied the defence beyond its intended scope of application, for example, where the accused has broken the law to protect an economic interest. As a result, the law’s resilience to socio-ecological changes is enhanced.

However, in the context of environmental crisis, several factors that create conditions favourable to the successful invocation of the defence could also render the law flexible to such an extent that positive norms might lose their prescriptive value. The law’s extension to previously unregulated civil emergencies through statutory frameworks backed by penal sanctions, as well as the increased unpredictability and violence of extreme weather events, multiplies the occasions in which the defence could be raised.

Yet the availability of necessity to environmental activists is the principal factor that could critically diminish the law’s prescriptive value and the resilience of normative frameworks. As science progresses in its ability to demonstrate that continued trends in environmental degradation push ecosystems to the brink of destruction, statutory frameworks for the sustainable management and protection of natural resources appear increasingly futile, and circumstances conform evermore closely to factual situations where the objective application of necessity’s requirements could result in the successful defence of illegal acts of civil disobedience committed against polluters. In other words, necessity may ultimately offer a defence against the application and enforcement of legal frameworks that, de facto, authorize catastrophic environmental destruction.

The possibility that necessity could exculpate political acts directed against the social order that the law should protect marks a point where the law becomes ineffective and loses the capacity to perform its function: this is the point where the application of legal rules undermines conformity with legal rules. Hence, a study of necessity in a context of environmental crisis lays bare the fundamental tension between a positivist conception of the rule of law and socio-political values, revealing subjective notions of the social good often veiled behind the neutral facade of legal regimes. From the perspective of environmental activists, insistence on the preservation of increasingly discredited legal frameworks for environmental management, despite their apparent failure, evidences the rule of law’s subordination to power structures serving particular interests.[154] If the rule of law becomes an instrument of political power, necessity evens the battlefield by sheathing political opposition in countervailing legalism.

In this context, a tribunal trying “eco-terrorists” for illegal acts committed to protect the environment in circumstances conforming to the defence of necessity will always uphold the rule of law, whatever its decision is: rejecting the defence protects the existing legal order, while accepting the defence fosters the objective implementation of legal rules. Equally, the court’s verdict will inevitably manifest a political choice: siding with values that are generally accepted by society and that underpin the existing legal order, or fostering a conception of the rule of law where the judiciary acts as a neutral arbiter that applies formal rules to resolve a conflict between divergent but equal interests by accepting the defence of necessity when its requirements are met.