A.  Introduction—Concept of Proportionality

1  Proportionality is a principle found in a number of different areas of both international and domestic law, including the law of armed conflict, the law of treaties, the law regarding the use of force, maritime delimitation law, and human rights law. As such, it has a number of different permutations according to the specific area in which it operates. However, as a general principle (General Principles of Law), proportionality means that a State’s acts must be a rational and reasonable exercise of means towards achieving a permissible goal, without unduly encroaching on protected rights of either the individual or another State.

2  Proportionality is often divided into three elements—suitability, necessity, and proportionality strictu sensu. Suitability requires that the measures in question are appropriate to the objective sought. Necessity provides that the objective can only be achieved by the measures in question; that is, if there is a choice between several suitable measures, then the least onerous measure must be chosen. Finally, the strictu sensu—or narrowest sense—proportionality element means balancing the effects of measures chosen against the objective sought, taking into account whether those effects are excessive according to those most affected. This is important when considering an objective that might have a highly restrictive outcome—for instance, in a human rights case. The more restrictive the objective may be, the justification for such restriction must be of high importance. Thus, the derogations from or serious limitation of certain human rights would need to be done for the more serious of reasons—such as grave questions of national security.

B.  Historical Development of the Concept

3  Some have traced the origins of the concept of proportionality back to the writings of Aristotle, who wrote in Nicomachean Ethics (Book V) of the idea of ‘distributive justice’—the idea that one must treat equal persons equally, unequal persons unequally, and that justice requires that the benefits that accrue from a common asset (such as property) must be distributed to individuals in proportion to their merit. A deliberative justice approach is essentially one of a proportional balancing—measuring competing claims based on context and merit (Engle at 4).

4  However, the concept of proportionality was developed more fully in the writings of Cicero, Augustine, and Aquinas, in relation to ‘just war’ and the law of self-defence. As outlined by Cicero, war as a tool of State policy was permissible only after all avenues of peaceful resolution had been explored. Cicero’s argument was developed by Saint Augustine (City of God) and Saint Thomas Aquinas (Summa Theologica), who further developed the idea that war was permissible if, among other factors, the armed conflict could be considered a proportional response to aggression: ‘whenever a thing is for an end, its form must be determined proportionally to that end; as the form of a saw is such as to be suitable for cutting … everything that is ruled and measured must have a form proportionate to its rule and measure.’

5  The most refined explanation of the concept came in the writings of Hugo Grotius, who enunciated six elements in his theory of ‘just war’: just cause, rightful intention, proper authority and public declaration, war as a last resort (necessity), probability of success, and proportionality of response to aggression. Thus, proportionality was key to nearly every stage of just war theory. Grotius added an additional element—not only was proportionality fundamental in decisions regarding initiating war, proportionality must also be considered in the conduct of the war itself. He argued in De Jure Belli ac Pacis (On the Law of War and Peace) that ‘no war should be undertaken, but where the hopes of advantage could be shewn to overbalance the apprehensions of ruin’.

6  Proportionality and the use of force again came into play in international law with the Caroline incident, which took place in 1837 during the Canadian rebellion against Britain. The rebels, including some American citizens based in Canada, had been receiving supplies and reinforcements from America by means of the steamer Caroline. The US authorities had been requested to stop the chain of supply, as these supplies were coming from America, thus violating the laws of neutrality. The US authorities were unable to halt supply; thus, in order to end the aggressive acts of the rebels, a British force entered the US, boarded the Caroline, and, setting her on fire, sent her over the US side of the Niagara Falls. Two US citizens were killed as a result and the US Secretary of State demanded that the British government demonstrate that its actions showed ‘a necessity of self-defence, instant, overwhelming, leaving no choice of means and no moment for deliberation’ (Parliamentary Papers [1842] in 30 British and Foreign State Papers 195, 201). Additionally, Webster argued that along with the requirement of ‘necessity of self-defence’, it must be shown that the local authorities ‘even supposing the necessity of the moment … did nothing unreasonable or excessive; since the act justified by that necessity of self-defence, must be limited by that necessity, and kept clearly within it’ (Parliamentary Papers at 202).

7  The question of proportionality in international law remained in the background for some time, prior to the adoption of the United Nations Charter. Proportionality was, however, being developed and embraced as a legal principle in domestic regimes, specifically Germany, which adopted the principle and test of proportionality to assess whether action taken by the police in their dealings with the citizenry were more intrusive than they needed to be in order to achieve their objective. Proportionality was then incorporated into administrative law and in regards to legislative action. However, the question of proportionality in international law did not come up again as a major issue until the Naulilaa Arbitration (Portugal v Germany), which looked at the question of reprisals under international law. In that instance, three German nationals were killed by officials at a Portuguese frontier post in Portuguese South West Africa. In response, the authorities in German South West Africa ordered the destruction of numerous frontier forts in Portuguese- controlled territory. In determining whether the German reprisal was legitimately carried out, the Arbitral Commission found that the German response was unlawful for, among other reasons, its disproportionate scope. The Commission acknowledged that there was no definitive doctrine of reprisals under international law that included the element of proportionality, but that ‘even if one admits that international law does not require that reprisals be measured approximately by the offence, one must certainly consider as excessive, and consequently illicit, reprisals out of all proportion to that act that has motivated them’ (Naulilaa Arbitration [Portugal v Germany] [1928] 2 RIAA 1012, 1028).

8  The concept of proportionality became fixed in international law with regards to resort to force with the adoption of the UN Charter in 1945. While the use of (and the threat of use of) force against the territorial integrity of another State is prohibited under the UN Charter (Art. 2(4)), the Charter nonetheless recognizes that individual or collective self-defence is permissible if an armed attack occurs against a member of the United Nations (Art. 51) (Use of Force, Prohibition of; Use of Force, Prohibition of Threat). However, while not stated in the Charter, it is accepted, and has been asserted by the International Court of Justice (ICJ) (see below para. 10), that any response to such an armed attack must be ‘proportional’.

C.  International Jurisprudence

9  The issue of proportionality has frequently come before the ICJ in cases regarding maritime delimitations. In cases such as the North Sea Continental Shelf Cases, the Continental Shelf Case (Tunisia/Libyan Arab Jamahiriya), the Gulf of Maine Case, and the Continental Shelf Case (Libyan Arab Jamahiriya/Malta), a key issue before the Court has been the question of whether there should be a relationship between the relative length of a State’s coastline and whether the amount of shelf awarded to that State should be proportional to their coastline. In North Sea Continental Shelf Cases, the Court stated that one of the factors considered was ‘the element of a reasonable degree of proportionality, which a delimitation carried out in accordance with equitable principles ought to bring about between the extent of the continental shelf areas appertaining to the coastal State and the length of its coast’ (at 54).

10  Another area where proportionality is a key determinant is in cases regarding the use of force. However, in this instance, proportionality is not strictly used as an ‘ends-means’ balancing test between competing interests over a single asset but rather as a means of limiting harm against others in situations of armed conflict. As noted above, the right to self-defence against an armed attack is itself subject to limitations and requirements. One of these is that any act in self-defence to an armed attack must itself be ‘proportional’ to that armed attack. In cases where the ICJ has had to look at questions of proportionality in self-defence, the ICJ has affirmed proportionality as a fundamental rule of customary international law. As stated by the ICJ in Legality of the Threat or Use of Nuclear Weapons (Advisory Opinion), ‘the submission of the exercise of the right of self-defence to the conditions of necessity and proportionality is a rule of customary international law’ (para. 41). The Court also affirmed the customary status of proportionality in self-defence in Military and Paramilitary Activities in and against Nicaragua (Nicaragua v United States of America) (‘Nicaragua Case’).

11  The Court has also addressed the issue of precisely what is a proportionate response to an armed attack. Higgins notes that the answer to the question ‘proportionate in respect of what?’ can be answered with ‘proportionate in relation to the injury being inflicted’ (Higgins 231). Thus, in the Nicaragua Case, the ICJ included the element of proportionality when looking at the non-forceful countermeasures held by the Court to be the appropriate response to low-level uses of force that did not meet the threshold of armed attack (Nicaragua Case at paras 210, 24; Higgins 231). The Court has also looked at measuring the scope of proportionality of countermeasures in the Oil Platforms Case and in Armed Activities on the Territory of the Congo (Democratic Republic of the Congo v Uganda).

12  The Court also uses a test of proportionality when looking at questions of peaceful countermeasures. The Court in the Gabčíkovo-Nagymaros Case (Hungary/Slovakia) put their approach concisely: ‘the effects of a countermeasure must be commensurate with the injury suffered, taking account of the rights in question’ (at 56). This approach has been affirmed by the International Law Commission’s Draft Articles on State Responsibility, in Art. 51 ( see also Art. 49 Draft Articles).

D.  Jurisprudence of the European Court of Human Rights (ECHR)

13  Proportionality balancing has been pivotal in numerous European Court of Human Rights (ECtHR) jurisprudence, including the cases Rasmussen v Denmark, Lithgow v United Kingdom, Gillow v United Kingdom, Fayed v United Kingdom, Mellacher v Austria, Pine Valley Developments Ltd and others v Ireland, Steel v United Kingdom, Mathieu-Mohin and Clerfayt v Belgium, Sporrong and Lönnroth v Sweden, and Open Door and Dublin Well Woman v Ireland, to name a few. Indeed, it is noteworthy that a considerable proportion of jurisprudence in the European Court originates from the UK. For some time, the UK courts were bound by a different standard to that of a proportionality/necessity balancing test. This often resulted in decisions coming into conflict with the ECHR—this was seen in cases such as Handyside v United Kingdom, Dudgeon v United Kingdom, Smith and Grady v United Kingdom, and Peck v United Kingdom. The situation was resolved in the late 1990s when the Human Rights Act (1998) (c 42 [UK]) incorporated the ECHR in UK law, and the House of Lords adopted proportionality as the standard for measuring necessity (in de Freitas v Permanent Secretary of Ministry of Agriculture, Fisheries, Lands and Housing).

E.  Jurisprudence of the World Trade Organization (WTO)

14  The World Trade Organization (WTO) came into force on 1 January 1995, as the replacement organisation for institutions established under the General Agreement on Tariffs and Trade (‘GATT’). Article XX GATT outlines a number of ‘General Exceptions’ to GATT, including measures which may be deemed necessary to: protect public morals; protect human, animal, or plant life or health; national treasures of artistic, historic, or archaeological value; and conserve exhaustible natural resources if such measures are made effective in conjunction with restrictions on domestic production or consumption, and with regards to importations or exportations of gold or silver and relating to the products of prison labour. In addition, there are ‘positive’ obligations on States under the Agreements on the Application of Sanitary and Phytosanitary Measures (‘SPS’) and on Technical Barriers to Trade (‘TBT’) (1867 UNTS 493), which set down criteria to ensure that domestic legislation of Member States does not place overly onerous constraints on international trade.

15  Proportionality in the WTO jurisprudence mainly centres on the balancing of trade versus non-trade values and interests. Case-law in the WTO has frequently focused on the public policy exceptions under Article XX, namely for the protection of human, animal, or plant life or health and conservation of exhaustible natural resources. Due to the wording of Article XX, which draws the distinction between measures ‘necessary to’ and measures ‘with regards to’, WTO jurisprudence with regards to proportionality has thus developed two different approaches. With regards to ‘necessity’, the Appellate Body (‘AB’) of the WTO has held that ‘determination of whether a measure, which is not “indispensable”, may nevertheless be “necessary” [under Article XX (d)] … involves in every case a process of weighing and balancing a series of factors which prominently include the contribution made by the compliance measure to the enforcement of the law or regulation at issue, the importance of the common interests or values protected by that law or regulation, and the accompanying impact of the law or regulation on imports or exports’. (Korea—Measures Affecting Imports of Fresh, Chilled and Frozen Beef para 163). This position was affirmed by the AB in Measures Affecting the Cross-Border Supply of Gambling and Betting Services and in Dominican Republic—Measures Affecting the Importation and Internal Sale of Cigarettes.

16  The ‘relating to’ test is somewhat less strict than the necessity test. As noted by the AB in Korea—Measures Affecting Imports of Fresh, Chilled and Frozen Beef, the term ‘relating to’ is ‘more flexible textually than the “necessity requirement”’. However, a ‘reasonable relationship’ between the means and ends must still be present, rather than an incidental or inadvertent connection. This position was affirmed in cases such as United States—Standards for Reformulated and Conventional Gasoline and United States—Import Prohibition of Certain Shrimp and Shrimp Products.

F.  Jurisprudence of the European Court of Justice (ECJ)

17  The first instance of the ECJ (European Union, Court of Justice and General Court) applying the principle of proportionality was in the Internationale Handelsgesellschaft Case, where it stated ‘a public authority may not impose obligations on a citizen except to the extent to which they are strictly necessary in the public interest to attain the purpose of the measure’ (at 1146). The Court was more explicit in the Schräder Case, where it stated that: ‘the principle of proportionality is one of the general principles of Community law. By virtue to that principle, measures … are lawful provided that [they] are appropriate and necessary for meeting the objectives legitimately pursued by the legislation in question … when there is a choice between several appropriate measures, the least onerous measure must be used’ (at 2269).

G.  Discussion of Current Status of Concept as it Operates in International Law

H.  Areas of Application

23  As noted above, the principle of proportionality has various areas of application, including standards for permissible weapons and rules regarding targeting in international humanitarian law; a standard for judicial review, a means by which one can balance competing interests that may come into conflict—such as trade interests and human rights considerations. The principle of proportionality is a concept that finds a place in numerous and diverse areas of international law, including trade, human rights, humanitarian law, maritime law, and law of treaties. As such, the principle varies according to the areas in which it is applied, but remains, essentially, a test for the balancing of interests and rights.

I.  Special Legal Problems

24  Despite the differing types of ‘proportionality’ test, a common element to all is the difficulty of determining the precise boundaries of what is proportional. This issue was highlighted in a report presented to the Prosecutor at the International Criminal Tribunal for the Former Yugoslavia (ICTY): ‘the main problem with the principle of proportionality is not whether or not it exists but what it means and how it is to be applied … it is much easier to formulate the principle of proportionality in general terms than it is to apply it to a particular set of circumstances because the comparison is often between unlike quantities and values’ (Final Report to the Prosecutor by the Committee Established to Review the NATO Bombing Campaign Against the Federal Republic of Yugoslavia, paras 48–50). This is most obvious when one considers proportionality testing in the context of armed conflict, that of balancing the loss of civilian lives and property versus the capture and/or destruction of a military objective.

25  In addition, there are problems with the application of proportionality tests by international courts and tribunals towards decisions of national bodies or institutions. An international body may not fully appreciate or understand the domestic issues in question; there is always the possibility of too great an incursion into national sovereignty and autonomy.

J.  Significance

26  The significance of the emergence and institutionalization of the principle of proportionality has been noted by some, such as Sweet and Matthews (at 160), as demonstrative of an emergent global constitutionalism. Proportionality assessment has become an overarching principle, diffused into a considerable number of international and domestic legal systems. As such, the proportionality principle becomes self-perpetuating; as proportionality is given significant consideration by judges, so too do States, lawyers, governmental officials, and all other players in the field become more adept at utilizing the lexicon of proportionality analysis. As noted by Sweet and Matthews, ‘to be a skilled social actor in the constitutional actor in the constitutional politics of Germany, Canada, Israel, the EU, the ECHR, or the WTO means learning to reason and deploy the language of [proportionality analysis]’ (at 161).