Time-Traveling Rules of Interpretation: Of ‘Time-Will’ and ‘Time-Bubbles’

Abstract

Treaty interpretation has important temporal aspects. However, international courts and tribunals regularly ignore the temporal dimension of treaty interpretation and instead pay a lip service to Articles 31–33 of the Vienna Convention on the Law of Treaties (VCLT), which they consider reflective of customary international law. In fact, these courts and tribunals sometimes treat the customary rules of treaty interpretation as if they have remained relatively unchanged throughout the ages, allowing judges and arbitrators to draw inspiration from the VCLT even when interpreting a treaty that predates 1980 (the date of the VCLT’s entry into force). While this method may be acceptable for relatively recent treaties, the question is whether it can hold water for the interpretation of 20th-century, 19th-century or even earlier treaties. Customary rules of treaty interpretation have not been immutable over time. Practice relating to the very existence as well as to the content of any rules of interpretation has been unsettled, and the claim of the rules’ immutability would be logically as well as systemically incoherent with the structure of the international legal system. The changeable nature of the rules of treaty interpretation produces intertemporal concerns and imposes limits as to what interpretative rules judges may apply. Unless the treaty parties agree differently, the presumption must be that the ‘time-will’ of the treaty parties is determinative of what rules of interpretation apply—whether those of the time of the treaty’s conclusion or those that exist today. Rules of interpretation can be ‘time-travelers’, but only if the treaty parties so will it.