Law, like medicine, is a practiced discipline, and the practice of international law is no exception. There are different contexts in which that practice unfolds. Here, our focus is on: (1) a specific form of practice, that of “advocates,” understood widely to include counsel advising or representing a party in legal proceedings, diplomats supporting a policy directive, and civil society activists advocating for legal causes; (2) engaging in different forms of legal advocacy, which can be organized analytically under three headings: legal advice and representation, diplomacy, and campaigning; and (3) in a specific context, that of advisory opinions and, more specifically, in the conception of requests for advisory opinions. Such requests are subject to different requirements according to the institutional setting through which they are channeled, but the most prominent and complex setting is that of requests for advisory opinions by the UN General Assembly to the International Court of Justice (ICJ). This is the setting we will refer to in our essay.

In most international tribunals, states alone can submit requests for advisory opinions.1 This is also true of requests to the International Tribunal for the Law of the Sea (ITLOS) sitting in plenary composition. The United Convention on the Law of the Sea (UNCLOS)2 does not expressly confer advisory jurisdiction on ITLOS. In practice, the Tribunal's advisory jurisdiction is governed by Article 138 of its Rules of Procedure, under which international agreements can empower entities to request advisory opinions of the Tribunal. The process leading to the making of advisory requests to ITLOS includes the drafting of legal questions and is largely political.3 In this process, sponsoring states have three goals: first, get requests before ITLOS; second, ensure that requests are not thrown out on grounds of jurisdiction or discretion; third, mobilize the constituency having stakes in the requests. This essay explores each of these goals.

The limited use of dispute settlement mechanisms under the UN Framework Convention on Climate Change and the Paris Agreement explains the recent upsurge in requests for advisory opinions on issues specific to climate change to international courts, namely the International Court of Justice (ICJ), the International Tribunal of the Law of the Sea (ITLOS), and the Inter-American Court of Human Rights. However, it is still unclear how these courts will answer the questions posed, and in particular whether they will coordinate or compete with each other. As the requesting states and bodies are well aware of this uncertainty, requesting an advisory opinion from three courts simultaneously was an ingenious (not ingenuous) strategy to clarify states’ obligations to mitigate or adapt to climate change through the international judiciary. This essay assesses how the parallel jurisdiction of courts in these cases presents an opportunity to enhance states’ obligations concerning climate change through requesting concurrent views on the same rules and obligations. It considers the potential for contradictory views between courts on the same obligations. Finally, the essay analyzes the extent to which these courts may compete or cooperate in their approach to the resolution of these issues.

Advisory opinions of the International Court of Justice (ICJ) are non-binding and lack operative clauses requiring compliance. At the same time, they reflect the ICJ's views as to rights and obligations of states under international law. In that sense they are not different from binding judgments and generate expectations of implementation of the Court's determinations. Although some states may reject an opinion, others have pursued implementation through the requesting organ, or through alternative political and legal means. And although it is not always easy to ascertain the effect of an opinion on states’ behavior, advisory opinions often have practical ramifications, even if they are not implemented.

In this essay, we analyze how different actors contribute to compliance with the advisory jurisdiction of the Inter-American human rights system. The essay briefly reviews the discussion around the binding force of, and compliance with, advisory opinions. It then analyzes how the holdings in advisory opinions issued by the Inter-American Court of Human Rights (IACtHR or Court) over the last forty years have had a notable impact on states and how different interstate actors, including the executive, the legislature, the national judiciary, and local regulatory bodies, ensure compliance.