International courts and tribunals must maintain a delicate balance between consent and coherence when they consider incidental questions as part of their dispute settlement function. There are compelling reasons, in the contemporary world of unprecedented complexity and interdependence, to instill coherence into dispute settlement procedures, so as to avoid the denial of justice. The exercise of jurisdiction over an “incidental question,” however, must not be forced to the point that it undermines the willingness of states to give their consent to such procedures.

In this essay, I discuss whether and to what extent the framing of the main dispute and incidental questions can have a gatekeeping function in relation to the jurisdiction and applicable law of a dispute settlement body. Recent cases have attached critical importance to the identification of the “real” main object of the dispute, and the “characterization” of claims to then determine which issues are incidental to the dispute, rather than focusing on which issues are within the tribunal's ratione materiae jurisdiction. Through an examination of selected case law, I argue that this “characterization approach” could in effect elevate a subjective framing of the “main” dispute to a jurisdictional gatekeeper. This approach introduces unnecessary evaluative determinations while obscuring normative clarity regarding the limits of consent-based jurisdiction and its relationship to incidentally applicable law.

Human rights courts and bodies do not rely on the concept of incidental jurisdiction. As far as I am aware, they never have. Given that these courts and bodies are in many ways typical examples of international courts, this is at first glance surprising. However, a closer look suggests that human rights bodies employ rival techniques to tackle the same problem to which incidental jurisdiction is supposedly responding. This essay sets out, first, that there is nothing unique about the institutional set up of human rights courts and human rights bodies in international law that might explain the absence of incidental jurisdiction. Second, I offer a plausible reconstruction of this absence. I argue that it is not only a rational response to the particular demands of human rights litigation, but that it may even be normatively preferable. The tension between dispute settlement and state consent is modified and heightened in international human rights law; this justifies treating incidental questions with the weight usually attached to the main issues of a case by turning them into questions of treaty interpretation. Third, I illustrate these rival techniques in two areas: jurisdiction in international human rights law, and cases involving armed conflicts.

Arbitral tribunals in investment treaty arbitration have not contributed much to the theoretical development of the concept of incidental jurisdiction, even though they have occasionally exercised it in practice. One possible explanation for their apparent reluctance to make explicit and greater use of the concept of incidental jurisdiction is the tendency to adopt a strict approach to jurisdiction governed by party consent. In this essay, I argue that incidental jurisdiction is not in tension with the consensual foundations of international jurisdiction when it is viewed as one inherent power of international courts and tribunals. Key to this argument is that incidental determinations are not binding, and therefore do not need to fall within party-defined jurisdictional limits.

International courts and tribunals have developed two criteria for the exercise of incidental jurisdiction: necessity and ancillarity. Yet the question of whether to make an incidental determination is not unique to the adjudicatory context. International organizations sometimes confront it as well. And their practice in dealing with this question suggests that the criteria of necessity and ancillarity alone are insufficient for assessing whether an incidental determination should be made.