International Relations ♦ Online 65 Va. J. Int’l L. Online 1 (2024)

Delimiting “Agreements” for International Law

DUNCAN B. HOLLIS

Agreements are central to many international law projects, including both treaty-making and the (rising) use of non-binding agreements. Yet, for all the attention states and scholars currently direct to differentiating between binding and non-binding agreements, there has been relatively little discussion of the antecedent inquiry—what constitutes an agreement in the first place? This short Essay calls for new efforts to define agreements for purposes of international law and international relations, focusing on two criteria—mutuality and commitment. Agreements require two (or more) participants just as they must exhibit some shared expectations regarding those participants’ future behavior. This definition provides important limiting principles by excluding certain binding instruments (e.g., unilateral declarations) as well as some non-binding ones (e.g., diplomatic “deliverables” that do not reflect shared commitments to future courses of conduct). Moreover, a focus on agreements foregrounds a salient category absent in most existing discourse—tacit agreements. Reflecting on why tacit agreements qualify as agreements can help highlight different methods (e.g., content-driven criteria, presumptions and defaults) to supplement (or substitute for) existing subjective and objective efforts to identify whether an agreement is binding under international law. For those concerned with the transparency of diplomatic deliverables, the efficacy of domestic approval procedures for international agreements, as well as the operation of both the law of treaties and the law of state responsibility, it will be necessary to develop a broader and deeper understanding of what agreements “are” alongside any efforts to identify and differentiate among their binding and non-binding forms.