The lawfulness of carbon border adjustment measures (CBAMs) under general international economic law and particular economic agreements is explored; specifically, if their international lawfulness can be determined by thinking of them as countermeasures necessary to implement climate change obligations. As there are no non-discriminatory obligations under customary international law, it is argued that CBAMs are lawful under general international law, but under particular international economic agreements they can be seen as countermeasures lawfully taken in response to breaching the obligation to curb GHG emissions, allowing their justification as a breach of primary non-discriminatory economic obligations, particularly the national treatment principle under the GATT and GATS. This shifts the burden of proving necessity/proportionality to the State in breach of the obligation. CBAMs are fundamentally lawful measures and can only give rise to compensation if it they are unnecessary/disproportionate. This chapter also assesses whether they can be thought of as erga omnes contractantes obligations under international economic agreements, particularly the GATT and the GATS.

The author starts by observing that discussions about the foundations and the limits of the powers of international courts, including those of the European Court of Human Rights (hereafter ECtHR), turn around the aims of achieving legal certainty, ensuring legitimacy and justice, and avoiding conflicting obligations which may emanate from different regimes of international law. The chapter reflects on these aims from the perspective of consent as the common basis of the main sources of international law, as listed in Article 38 of the Statute of the International Court of Justice. Proceeding from the case law of the ECtHR, the chapter explores how the recent work of the International Law Commission conceives the role of consent in respect of the main sources of international law, and whether the jurisprudence of the ECtHR remains within the framework of general international law so enunciated.

EU law has a complex relationship with the concept of peremptory norms. On the one hand, the case law of the ECJ shows a pattern of ‘avoidance’ of peremptory norms of general international law, namely a reluctance by this Court to consider the legal effects of such norms in cases where they may be relevant. This is clear in the Kadi and Front Polisario/Western Sahara sagas. On the other hand, EU law has ‘assimilated’ the concept of peremptory norms more than it may seem at first sight. Indeed, it may be affirmed that EU law has its own system of peremptory norms. Such as system is based on norms and principles that have some of the defining features of the peremptory norms of general international law (including a system of enhanced responsibility for serious breaches of such peremptory norms). While, in analytical terms, this characterization does not matter much for EU law, it is certainly critical to the proposition that general international law does not exclude the existence of a regional jus cogens.

By considering effectiveness beyond formal normative sources and titles of the subjects implicated in the territorial situation, international human rights law is interpreted and applied in a manner that renders human rights practical and effective in matters of the applicability and scope of international human rights obligations, international responsibility for their breaches and international monitoring mechanisms. This normalising role of international human rights law has an important limit, the rights of States under general international law, and three hidden consequences: the effective use of the residual powers by the territorial State; the consolidation of the subject de facto controlling the area; and an activism required from multiple actors.

Chapter 7 discusses the law applicable to shareholder treaty claims. It argues in favour of an integrated approach to the applicable law, that is, one that gives proper weight not only to the applicable IIA provisions but also to general international law and national law. The reason for this is, first, that IIA provisions, including applicable law clauses, commonly require the application of the three sources of law. Second, overlaps between international and national law claims call for consideration and application of this latter legal system. And third, admissibility determinations are not focussed on the scope of treaty provisions containing consent to international jurisdiction but on the content of specific claims (thus often involving substantive aspects).