A.  Concept and Origin

1  In the context of inter-State relations, the maxim sic utere tuo ut alienum non laedas (use your own property in such a manner as not to injure that of another) stands for the proposition that one State’s sovereign right to use its territory is circumscribed by an obligation not to cause injury to, or within, another State’s territory.

2  The maxim is generally said to have its origins in Roman law, although this account has been challenged by commentators who argue that the exact phrase cannot actually be so traced. Similarly, while the notion is commonly said to exist in national legal regimes governing private property rights, some observers caution that the maxim itself has seldom found expression in national law. It has been invoked in some Anglo-American cases on neighbourhood nuisances but has not been specifically cited in civil law settings. Be that as it may, for present purposes it will suffice to say that the debate concerns the origins of the maxim itself. There is general agreement that comparable concepts can indeed be found in Roman property rules and in contemporary civil and common law systems, as well as in other legal traditions such as in Islamic or Jewish law.

B.  Purpose and Meaning

3  The fact that there exist principles that are ‘comparable’ to the sic utere tuo maxim (or that express related ideas) highlights the difficulties that arise in identifying the precise meaning of the maxim. It is at times used interchangeably with—or is not sharply distinguished from—related concepts such as abuse of rights or good neighbourliness (Neighbour States). Some commentators see the maxim of sic utere tuo as the foundation for the concept of abuse of rights. However, the majority view appears to be that it is the notion of abuse of rights that anchors the sic utere tuo principle, the latter being a particular manifestation of the former, broader concept. The concept of good neighbourliness, too, is seen by many commentators as an expression of the abuse of rights principle, serving to restrict the exercise of territorial rights. In turn, good neighbourliness is usually said to be closely related to—but not identical with—the sic utere tuo maxim, amplifying or explaining it.

4  All three concepts have in common the idea that a State’s use of its territory is inherently limited by the rights of other States not to be harmed in the use of their territory. Yet this right not to suffer transboundary harm is also limited by a duty to tolerate certain interferences—a duty that is coextensive with the neighbouring State’s right to use its territory. For some commentators, this duty to tolerate flows from the good neighbourliness principle rather than the sic utere tuo maxim. Similarly, it is the concept of good neighbourliness rather than the maxim of sic utere tuo that gives rise to related procedural duties such as those of notification and consultation in relation to transboundary harm.

5  In any event, the basic idea underpinning the maxim is that of a balancing of conflicting sovereign rights. This balancing requirement arguably inheres in the very notion of sovereign equality (States, Sovereign Equality) and the practical as well as conceptual impossibility of absolute territorial sovereignty and territorial integrity (see also Territorial Integrity and Political Independence). Thus, from States’ sovereign equality flows the idea that ‘where … the exercise of a sovereign right is bound to conflict with similar rights of an equal rank, insistence on individual rights must be considered unreasonable and reprehensible’ (Handl 56)—an abuse of rights that is encapsulated both in the maxim of sic utere tuo and in the concept of good neighbourliness.

6  The general idea of the mutual limitation of sovereign rights was also articulated in the Palmas Island Arbitration, when the arbitrator, Max Huber, held that ‘[t]erritorial sovereignty … has as corollary a duty: the obligation to protect within the territory the rights of other States, in particular their right to integrity and inviolability … ’ (Island of Palmas [Netherlands v United States of America] 839). The International Court of Justice (ICJ) built on the same idea when it opined in the Corfu Channel Case that it was ‘every State’s obligation not to allow knowingly its territory to be used for acts contrary to the rights of other States’ (Corfu Channel [United Kingdom of Great Britain and Northern Ireland v Albania] [Merits] 22).

7  Against the backdrop of general agreement on these broad propositions, the central question with respect to the content of the sic utere tuo maxim concerns the criteria according to which the mutual limitation of sovereign rights occurs. The question is as important as it is complex. Notwithstanding its absolute phrasing, the mere causation of transboundary harm does not transgress the sic utere tuo maxim. But is the threshold criterion subjective or fault-based? Or is it objective, focusing on the severity of the harm inflicted on the neighbouring State? Or a combination of the two? It is difficult to point to examples in either domestic or international law on the basis of which a categorical answer could be given to these threshold questions.

8  Civil law systems tend to rely on concepts of good neighbourliness and abuse of rights rather than the sic utere tuo principle as such. As a result, a subjective criterion, often expressed in terms of good faith (bona fide), enters into the determination of the limits imposed on property use. In common law systems, the maxim has been invoked both to require that ‘due care and caution’ be exercised to avoid injury to neighbouring property (Fleming v Lockwood 963) and to suggest that injury, inflicted ‘however innocently’, can give rise to liability (Rylands v Fletcher 341; see also Liability for Environmental Damage; Liability for Lawful Acts). However, the common law of nuisance more generally speaking tends to focus on the unreasonable nature of the interference rather than of the conduct that occasioned it.

9  At the international level, the conceptualization of situations that involve transboundary injury relies on the notions of sovereignty, good neighbourliness, abuse of rights, and sic utere tuo. As noted above, it is not always clear on which of these concepts reliance is placed, making it difficult to identify general threshold criteria of the sic utere tuo maxim itself with certainty. The clearest manifestation, and most detailed elaboration, of the sic utere tuo idea in international law is the no harm rule, which has evolved in the contexts of the use of transboundary resources and environmental impacts.

10  Indeed, the sic utere tuo maxim has been said to have found its way into international law in the context of transboundary rivers, giving rise to principles of equitable utilization of shared resources and to a prohibition on harmful transboundary impacts. It was in the context of air pollution, however, that the no harm rule was most famously expressed (Air Pollution, Transboundary Aspects). The 1941 Trail Smelter Arbitration concerned air pollution originating from a smelter located in the Canadian province of British Columbia and causing damage to livestock and farmland in the US State of Washington. The arbitral tribunal confirmed the existence of the no harm rule in international law and specified that the injury in question had to be ‘of serious consequence’ and ‘established by clear and convincing evidence’ (Trail Smelter [United States of America v Canada] 1965).

11  The no harm rule has since been reaffirmed in numerous instruments dealing with international environmental matters (see also Hazardous Substances, Transboundary Impacts; Hazardous Wastes, Transboundary Impacts). For example, according to Principle 21 of the 1972 Stockholm Declaration of the United Nations Conference on the Human Environment and the similarly phrased Principle 2 of the 1992 Rio Declaration on Environment and Development, States have ‘the sovereign right to exploit their own resources … and the responsibility to ensure that activities within their jurisdiction or control do not cause damage to the environment of other States or of areas beyond the limits of national jurisdiction’ (Stockholm Declaration [1972] and Rio Declaration [1992]). The no harm rule has also been endorsed by a large number of multilateral environmental agreements (‘MEAs’; Environment, Multilateral Agreements), including such important agreements as the Convention on Long-Range Transboundary Air Pollution ([adopted 13 November 1979, entered into force 16 March 1983] 1302 UNTS 217), the Vienna Convention for the Protection of the Ozone Layer ([adopted 22 March 1985, entered into force 22 September 1988] 1513 UNTS 324; Ozone Layer, International Protection), the United Nations Framework Convention on Climate Change ([adopted 9 May 1992, entered into force 21 March 1994] 1771 UNTS 107; Climate, International Protection), the Convention on Biological Diversity ([adopted 5 June 1992, entered into force 29 December 1993] 1760 UNTS 79; Biological Diversity, International Protection), and the Convention on the Law of the Non-Navigational Uses of International Watercourses ([adopted and opened for signature 21 May 1997, entered into force 17 August 2014] (1997) 36 ILM 700; International Watercourses, Environmental Protection).

12  Although these instruments’ articulations of the no harm rule do not explicitly address the severity of harm, they have been read by States and scholarly commentators as requiring that the harm be of some significance. Similarly, even without explicit reference to a fault requirement, it is generally understood that the no harm standard in international environmental law is one of due diligence. The Draft Articles on Prevention of Transboundary Harm from Hazardous Activities of the International Law Commission (ILC) reflect this assessment. The commentary to Art. 3 Draft Articles, which stipulates that ‘States shall take all appropriate measures to prevent significant transboundary harm’, notes that the article ‘is based on the fundamental principle sic utere tuo ut alienum non laedas’ and that the standard of conduct is due diligence (UN ILC ‘Draft Articles on Prevention of Transboundary Harm from Hazardous Activities, with Commentaries’ [2001] vol II part II UNYBILC 148 at 153–54). Over the years, some writers have argued for a strict liability standard in cases involving environmental harm. However, such a standard has not established itself within general international law and the 1972 Convention on International Liability for Damage Caused by Space Objects remains the only clear example of a treaty-based strict liability regime for States (see also Outer Space, Liability for Damage; Spacecraft, Satellites and Space Objects). Instead, some treaties impose strict liability on private actors, an approach that is also proposed by the ILC in its 2006 Draft Principles on the Allocation of Loss in the Case of Transboundary Harm Arising out of Hazardous Activities ([2006] GAOR 61^st Session Supp 10, 106).

13  But the expression that the no harm rule was given in the Stockholm and Rio Declarations, as well as its endorsement in MEAs that deal with regional or even global issues, also reflect an expansion of the rule. Today it protects not just the territorial integrity of neighbouring States, but also the environment of all States as well as the global commons.

14  It is more difficult to say to what extent the sic utere tuo maxim or the no harm rule apply to other types of transboundary impacts than those involving natural resources or the environment (see also Conservation of Natural Resources). The basic proposition expressed in the Island of Palmas Case would seem to be broadly applicable. Related ideas have found expression in a range of contexts, connected only by the notion that States must consider the rights of other States in exercising their territorial sovereignty. For example, the decision of the Permanent Court of International Justice (PCIJ) in The ‘Lotus’ (France v Turkey) (Lotus, The) concerned the assertion of jurisdiction over crimes committed by a foreign national on the high seas. And in the aforementioned Corfu Channel Case, the ICJ considered a State’s duty to protect the rights against harm occasioned by actions undertaken within its borders. It is less clear, however, whether these broadly applicable notions can be traced back to the sic utere tuo maxim or simply to the mutual limitation of sovereign rights. It has been argued, for example, that sic utere tuo constitutes a ‘general duty to prevent and to minimize the risk of transboundary harm’ and as such is applicable to diverse impacts, including international terrorism (Dupuy and Hoss 228). However, concrete applications of the sic utere tuo maxim or the no harm rule in contexts other than international environmental law appear to be rare. One set of examples may be found in early agreements adopted with respect to broadcasting, such as the 1927 International Radiotelegraph Convention ([adopted 25 November 1927, entered into force 1 January 1929] 84 LNTS 97) or the 1932 International Telecommunication Convention ([adopted 9 December 1932, entered into force 1 January 1934] 151 LNTS 4; see also Broadcasting, International Regulation).

C.  Legal Status

15  The vast majority of observers share the assessment of the ICJ, expressed in its 1996 Legality of the Threat or Use of Nuclear Weapons (Advisory Opinion) (Nuclear Weapons Advisory Opinions), that ‘the general obligation of States to ensure that activities within their jurisdiction and control respect the environment of other States or of areas beyond national control is now part of the corpus of international law relating to the environment’ (at para. 29). However, it is noteworthy that this formulation, repeated in the Gabcíkovo-Nagymaros Case (Hungary/Slovakia) (para. 53), differs from the wording contained in the Stockholm and Rio Declarations and in other above-mentioned international instruments. Commentators have read the reference to ‘jurisdiction and control’ rather than ‘jurisdiction or control’ as ‘limiting extraterritorial application’ of the rule (Brown Weiss 340). Similarly, the Court’s decision to refer to an obligation to ‘respect the environment of other States or of areas beyond national control’ rather than not to ‘cause damage’ has been read as imposing ‘a broader, less precise obligation’ (Brown Weiss 340).

16  In any event, whether the maxim of sic utere tuo has acquired the status of customary international law outside of the specific context of international environmental law and beyond the parameters of its no harm rule is more difficult to say. While some observers consider that it has, others express doubts given the lack of clear State practice and opinio iuris and the blurred boundaries between the maxim and the related concepts of abuse of rights and good neighbourliness. For the same reasons, opinions differ widely on whether or not the sic utere tuo maxim could be said to be a general principle of law within the meaning of Art. 38 (1) lit. c Statute of the International Court of Justice (General Principles of Law).

D.  Conclusion

17  The maxim of sic utere tuo ut alienum non laedas holds a somewhat paradoxical place in international law. Its origins, purpose and meaning, and status in international law are surprisingly difficult to pin down with certainty. Nonetheless, the idea expressed by the maxim has shaped international legal reasoning and has found expression in a number of important judicial decisions as well as in a range of international legal instruments, notably in the context of international environmental law. Thus, regardless of its legal status and regardless of the precise nature of its relationship to the general notion of sovereign equality or to the related concepts of abuse of rights and good neighbourliness, the sic utere tuo maxim has come to be firmly woven into the fabric of international law. It has been highly influential and is rightly hailed as a foundational principle of international law.