What are States’ duties and obligations vis-à-vis other states and their own population in the climate change context?
International law primarily determines the rights and duties of States in their dealings with other States. The main sources of States’ obligations related to climate change are the United Nations Framework Convention on Climate Change (UNFCCC), the Kyoto Protocol, as well as those that may be derived from general international law. International law regulates States’ conduct in relation to their own population only in limited instances. These limited instances are principally confined to the area of human rights law. States’ obligations in the human rights field are context specific and depend on a number of variables. This brief summarises States’ obligations under general international law and human rights law that are most relevant from a climate change perspective.
UNFCCC Parties are expected to comply with their extant international obligations, including those under general international law and human rights law, when they implement their obligations under the climate regime. UNFCCC Parties have not provided specific guidance on how States should take human rights into account when construing, developing, and operationalizing their commitments to combat climate change. The extent of the application and enforcement of protected human rights in any given context will depend on a host of national circumstances, and, most significantly, on the human rights instruments any given country has ratified.
THE SOURCES OF STATES’ DUTIES AND OBLIGATIONS
Most international law obligations derive from treaties. Treaties only create obligations for contracting States and the duties and obligations of States therefore vary according to which treaties they have ratified. The United Nations Framework Convention on Climate Change (UNFCCC) and the Kyoto Protocol have been almost universally ratified and therefore are the most important sources of States’ duties and obligations in relation to other States on climate change. These obligations are to be interpreted in the light of guidance that Parties adopt in the context of the decisions of treaty bodies, such as the Conference of the Parties (COP) of the UNFCCC and the Conference of the Parties serving as the meeting of the Parties to the Kyoto Protocol (CMP).
In relation to duties and obligations owed to a State’s own population, the most important sources of State obligations are the two ‘foundational’ human rights treaties (the International Covenant on Civil and Political Rights and the International Covenant on Economic, Social and Cultural Rights), both of which have been widely, albeit not universally, ratified. Other human rights instruments contain obligations that are relevant in relation to climate change. Although States may be parties to the same treaties, they may not have the same obligations, as States’ obligations toward the fulfilment of some human rights may be constrained by limited resources.
Customary international law may also be a source of legal obligations that are relevant for the present purposes, even though the customary status of specific norms is often contentious. Customary international law is derived from the consistent practice of States accompanied by opinio juris – the conviction of States that the consistent practice is required by a legal obligation. In addition to direct evidence of State behaviour, judgments of international courts as well as the results of academic investigation have traditionally been looked to as persuasive sources of international custom.
DUTIES AND OBLIGATIONS OWED TO STATES
Principle of sustainable development
While sustainable development may be regarded as a principle of international law  and, according to some, even customary international law, the International Court of Justice has more cautiously referred to it as an ‘international objective.’The UNFCCC contains a formulation of the principle of sustainable development and an enunciation of Parties’ right to sustainable development. The ILA has suggested that the principle of sustainable development requires that policies and measures taken in response to climate change integrate environmental, economic and social matters.
The obligation of prevention
Customary international law obliges States 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. The principle of prevention has its origins in the due diligence that is required of a State in its territory. The obligation of prevention obliges a State ‘to use all the means at its disposal in order to avoid activities which take place in its territory, or in any area under its jurisdiction, causing significant damage to the environment of another State’. The ILA has suggested that this obligation be interpreted to include damage through climate change.
The precautionary principle
In accordance with the precautionary principle, States must take measures to anticipate or prevent damage, without waiting for conclusive scientific proof, where there is a reasonably foreseeable threat of serious or irreversible damage. The precautionary principle is closely linked with the obligation of prevention. The main difference is that the precautionary principle operates before scientific evidence is conclusive, whereas the duty of prevention is directed to situations of harm and risk that are known or knowable. The ILA has suggested that in the climate context the principle may be interpreted in the sense that, where there is a reasonably foreseeable threat of serious or irreversible damage, measures to anticipate, prevent or adapt to climate change should be taken, without waiting for conclusive scientific proof of that damage. 
The requirement of environmental impact assessment
Environmental impact assessment is a means for considering potential environmental harm in decision-making process. States are obliged under general international law to undertake such assessment where there is a risk that a proposed activity may have a significant adverse impact in a transboundary context, in particular, on a shared resource. The ILA has specifically emphasised the requirement of EIA as a means to facilitate the interpretation of climate law in light of other relevant international law, such as the law of the sea.
The principle of cooperation
States have the duty to cooperate with one another in the various spheres of international relations, in order to maintain international peace and security and to promote international economic stability and progress, the general welfare of nations, as well as to conserve, protect and restore the health and integrity of the Earth’s ecosystem. The scope and status of the principle under customary law is controversial. The ILA has suggested that in the climate context the principle of cooperation be interpreted to mean that States cooperate with each other and competent international organisations in good faith to address climate change and its adverse effects.
The principle of equity
Equity is expressly mentioned in the principles guiding Parties in achieving the objective of the UNFCCC as the basis for action to protect the climate system. A lively debate presently concerns the appropriate principles to determine equitable allocation in the climate regime, e.g. whether decisions should be based on need, capacity, prior entitlement, ‘just deserts’, the greatest good for the greatest number, or strict equality treatment. The ILA has suggested that the reference to equity in the climate regime be interpreted to mean that States protect the climate system on the basis of equity, which inter alia implies that developed countries take the lead in combating climate change, whereas all States must protect the climate system in a manner that equitably balances the needs of present and future generations.
The principle of common but differentiated responsibilities
The principle of common but differentiated responsibilities has been described as the core distributive paradigm and the main operationalization of equity in the climate regime. The interpretation of the principle in international law is not univocal, and has engendered diverse arrangements concerning the allocation of obligations amongst States in international environmental agreements (e.g. obligations in the Kyoto Protocol vis-à-vis obligations in the Montreal Protocol). According to the ILA, States shall protect the climate system in accordance with their common but differentiated responsibilities and respective capabilities, such as their differing contributions to climate change, their differing technological, financial and infrastructural capabilities, as well as diverse economic fortunes and other national circumstances.
The principle of systemic integration
According to the so-called principle of ‘systemic integration,’ a treaty is to be interpreted in light ‘of any relevant rules of international law applicable between the Parties.’ When creating new obligations, States are thus assumed not to derogate from their obligations, as embodied in any rules of international law that are both ‘relevant’ and ‘applicable in the relations between the Parties. This interpretative rule is based upon the principle of good faith, albeit the existence of an actual principle of ‘systemic integration is debatable. In the context of climate change, the ILA has argued that, in order to effectively address climate change and its adverse effects, States shall formulate, elaborate and implement international law relating to climate change in a mutually supportive manner with other relevant international law.
DUTIES AND OBLIGATIONS OWED TO A STATE’S OWN POPULATION
UNFCCC Parties are expected to comply with their extant international obligations, including those concerning human rights, when they implement their obligations under the climate regime. Numerous human rights will be affected by the consequences of climate change. Specific attention has been drawn to the potential of procedural rights to engender greater legitimacy in climate governance, and, more generally, to the potential of human rights to guide climate law and policy-making. UNFCCC Parties have not provided specific guidance on how States should take human rights into account when construing, developing, and operationalizing their commitments to combat climate change.
The application of obligations to protect human rights in the context of climate change is subjected to some limits, as qualifying the effects of climate change as human rights violations poses a series of difficulties, including that of ‘disentangling complex causal relationships,’ as well as addressing projections about future impacts.The extent of the application and enforcement of protected human rights in any given context will depend on a host of national circumstances, and, most significantly, on the human rights instrument any given country has ratified. Furthermore, as a general rule, States only have to fulfill human rights obligations within their own territories. The extraterritorial relevance of human rights obligations may, however, arise when a State exercises control, power, or authority over people or situations outside its own territory.
The right to life
The right to life imposes wide-ranging obligations on States to ensure human life and adequate living conditions. The right must be implemented in a holistic manner and is closely related to other rights, such the right to food, water, health and housing.Climate change will pose direct and indirect threats to human lives that will affect the obligations of States, such as the obligation to prevent malnutrition and epidemics. Some human rights bodies have also linked the right to life with the obligation on States to ensure a healthy and safe environment.
The right to adequate food
The right to adequate food includes the right of everyone to be free from hunger. It further encompasses access and availability of adequate food, including through the possibility for feeding oneself from land or other natural resources. States are under an obligation to secure this right and to take necessary action to alleviate hunger, which might occur as a result of climate change.
The right to water and sanitation
The rights to water and to sanitation impose specific legal obligations, which climate change policy responses must take into account. The human right to water means that everyone has the right to sufficient, safe, acceptable, physically accessible and affordable water for personal and domestic uses, without discrimination. The right to sanitation means that everyone has the right to access to sanitation which is safe, hygienic, secure, socially and culturally acceptable, and that provides privacy and ensures dignity, without discrimination.
The right to health
The right to health implies the enjoyment of, and equal access to, appropriate health care and, more broadly, to goods, services and conditions which enable a person to live a healthy life. Underlying determinants of health include adequate food and nutrition, housing, safe drinking water and adequate sanitation, and a healthy environment. States are under an obligation to protect the right to health in the face of climate change will require comprehensive measures, including mitigating the adverse impacts of global warming on underlying determinants of health and giving priority to protecting vulnerable individuals and communities.
The right to adequate housing
The right to adequate housing has been defined as ‘the right to live somewhere in security, peace and dignity’. Climate change will affect the right to adequate housing in several ways and States are under an obligation to ensure rights to adequate housing, among others by protecting housing from weather hazards and to provide shelter and disaster preparedness in cases of displacement.
The right to self-determination
The right to self-determination is a collective right, whichincludes the right of a people not to be deprived of its own means of subsistence, and the obligation of States to promote the realization of the right to self-determination. Climate Change will have implications for the right to self-determination (e.g. by disappearance of island States) as well as for the full range of human rights for which groups depend on the State for their protection.
Obligations owed to specific groups
The effects of climate change will affects many groups to which States may have special duties. This among others includes women, children, persons with disabilities, indigenous peoples, stateless people and refugees. These groups enjoy all of the human rights mentioned above, but States may also owe special obligations to these groups depending on their treaty commitments.
ILO Convention 169 provides a series of rights specific to indigenous peoples, including the requirement that they be consulted through appropriate procedures whenever considering legislative or administrative measures that may affect them directly, such as activities carried out on their traditional lands. States must furthermore establish means by which indigenous peoples can freely participate, to at least the same extent as other sectors of the population and at all levels of decision-making, in bodies responsible for policies and programmes that concern them. Consultations must be undertaken in good faith and in a form appropriate to the circumstances, with the objective of achieving agreement or consent to the proposed measures.Whenever possible, indigenous peoples must participate in the benefits of such activities and receive compensation for any damage sustained.
Only few States have ratified ILO Convention 169. However, most parties to the UNFCCC have supported the adoption of the UN Declaration on the Rights of Indigenous Peoples (UNDRIP). UNDRIP does not affirm ‘special rights’ which are separate from the fundamental rights in the specific circumstances of indigenous peoples, but rather builds upon existing human rights. The Declaration recognises indigenous peoples’ right to determine their own economic, social and cultural development and to manage their natural resources. States are required to cooperate in good faith with the indigenous peoples concerned through their own representative institutions in order to obtain their free prior and informed consent (FPIC), “particularly in connection with the development, utilisation or exploitation of mineral, water or other resources”. UNDRIP requires FPIC also with regard to all legislative or administrative measures that may affect indigenous peoples. The requirement of consent has been interpreted in the sense to entail that indigenous peoples be empowered to ‘effectively determine the outcome of decision-making that affects them, not merely a right to be involved in such processes.’
A report by the ILA has argued that indigenous peoples’ right to FPIC may be regarded as part of customary international law.The latter conclusion seems premature. Some legal consequence may nevertheless be derived from the inclusion of FPIC in UNDRIP. As a UN General Assembly Resolution, the Declaration does not impose legally binding obligations on members of the United Nations. However, it no doubt provides an authoritative statement of the rights of indigenous peoples, which has been viewed as an expression of a ‘commitment to its provisions’ by the United Nations and its member States’ which should be viewed ‘within the framework of the obligations established by the United Nations Charter to promote and protect human rights on a non-discriminatory basis.’
 Cf. e.g. C Voigt, Sustainable Development as a Principle of International Law: Resolving Conflicts Between Climate Measures and WTO Law (Leiden, 2009).  V Barral, ‘Sustainable Development in International Law: Nature and Operation of an Evolutive Legal Norm’ (2012) 23 EJIL 377, at 388. Pulp Mills on the River Uruguay (Argentina v. Uruguay), ICJ Reports (2010) 14, para.177.  Cf. UNFCCC, Article 3.4.  ILA (2014), Draft Article 3.3.  This principle has been acknowledged in a series of cases, starting with Trails Smelter, Arbitral Trib., 3 UN Rep. Int’l Arb. Awards 1905 (1941), p. 1965. See also, Legality of the Threat or Use of Nuclear Weapons, Advisory Opinion, ICJ Reports 1996 (I) 226, para. 29; and Pulp Mills on the River Uruguay (Argentina v. Uruguay), ICJ Reports (2010) 14, para. 101. The scope of the principle has been expanded beyond the transboundary context in Principle 21 of the Declaration of the United Nations Conference on the Human Environment (Stockholm Declaration) (1972) and in Principle 2 of the Rio Declaration on Environment and Development (1992).  Corfu Channel (United Kingdom v. Albania), Merits, Judgment, ICJ Reports (1949), para. 22.  Pulp Mills on the River Uruguay (Argentina v. Uruguay), ICJ Reports (2010) 14, para. 101  ILA (2014), Draft Article 7a.  See e.g. Responsibilities and Obligations of States Sponsoring Persons and Entities with respect to Activities in the Area, Advisory Opinion of the Seabed Disputes Chamber of the ITLOS, Case No 17, (2011), para. 131. Rio Declaration, Principle 15.  ILA (2014), Draft Article 7b.  Declaration on Principles of International Law concerning Friendly Relations and Cooperation among States in Accordance with the Charter of the United Nations, UNGA Res. 2625 (XXV) (1970), principle 4.  Rio Declaration on Environment and Development (1992), Principle 7. UNFCCC, Article 3.1.  S Humphreys, ‘Competing Claims: Human Rights and Climate Harms’ in S Humphreys, Human Rights and Climate Change (Cambridge University Press, 2010) 37, at 49 (citing Shelton, 2007).  See e.g. S Kallbekken, H Sælen and A Underdal, Equity and spectrum of mitigation commitments in the 2015 agreement (Nordic Council of Ministers, 2014), p. 9; and F Soltau, Fairness in International Climate Change Law and Policy (Cambridge University Press, 2009) at 187.  S Humphreys, ‘Competing Claims: Human Rights and Climate Harms’, in Stephen Humphreys (ed.), Human Rights and Climate Change (Cambridge University Press, 2009) 37-68, at 47: ‘the search for equitable solutions under conditions of CBDR seems intended to compensate for the shortcomings of formal equality under law by acknowledging the reality that substantive differences exist between equally sovereign States’ (emphasis added). See also H Winkler and L Rajamani, ‘CBDR&RC in a Regime Applicable to All’ (2014) 14 Climate Policy 102, at 104; and W Scholtz, ‘Equity as the basis for a future climate regime’ 42(2) The Comparative and International Law Journal of Southern Africa (2009) 166, at 171. International Law Commission, Fragmentation of International Law: Difficulties arising from the Diversification and Expansion of International Law, Report of the Study Group of the International Law Commission finalized by Martti Koskenniemi (2006) UN Doc. A/CN.4/L.702, at 410-480.  Vienna Convention on the Law of Treaties (1969), Article 31.3(c).  Vienna Convention on the Law of Treaties (1969), Article 31.1. In this sense, cf. for example OK Dörr and K Schmalenbach (eds), Vienna Convention on the Law of Treaties: A Commentary (Springer 2012), at 561.  Birnie et al., for example, refer to systemic integration by using the term ‘technique’. P Birnie, A Boyle, and C Redgwell, International Law and the Environment (Oxford University Press, 2009), at 19. For a review of arguments, see A Lindroos and M Mehling, ‘From Autonomy to Integration – International Law, Free Trade and the Environment’ (2008) 77 Nordic Journal of International Law 253, at 268-9, where the authors note that international case law provides ‘a weak basis for an actual principle of systemic integration’, remarking how it is impossible to draw a consistent picture of the extent to which it would necessitate consideration of other norms of international law.’  L Rajamani, ‘The Increasing Currency and Relevance of Rights-Based Perspectives in the International Negotiations on Climate Change’ (2010) 23 Journal of Environmental Law, at 407-419; see also S Caney, ‘Climate Change, Human Rights and Moral Thresholds’ in Humphreys, Human Rights and Climate Change 69, at 86-90.  The right to life is explicitly protected in ICCPR, Article 6 and in other human rights instruments. With regard to climate change, see generally A/HRC/10/61, paras. 21-24.  CESCR, General Comments No. 12 (1999) On the Right to Adequate Food, para. 4, and No. 14 (2000) On the Right to the Highest Attainable Standard of Health, para. 4.  The right to food is explicitly mentioned in ICESCR, Article 11 and in other human rights instruments. With regard to climate change, see generally A/HRC/10/61, paras. 25-27.  While not explicitly mentioned in ICESCR, the right is seen to be implicit in Articles 11 and 12.  The right to health is explicitly mentioned in ICESCR Article 12.  The right to adequate housing is explicitly mentioned in ICESCR Article 12.  See generally A/HRC/10/61, paras. 35-38.  The right to self-determination is explicitly mentioned ICCPR and ICESCR Article 1. See A/HRC/10/61, paras. 51-54. A/HRC/9/9, para.41.