Under which conditions and to what extent can subsequent State practice legitimately influence the interpretation or even modify international treaties? This issue of general international law has been on the European Court of Human Rights’ agenda for quite some time and is ongoing as evidenced in Hassan v The United Kingdom. While State practice has traditionally played a role in the interpretation of the European Convention on Human Rights in its dynamic interpretation, the Court’s methodology to determine under what circumstance and to what extent State practice is able to affect the scope and meaning of the Convention remains uncertain. This chapter develops a general theoretical framework, which rationalizes the normative value of subsequent practice in the context of human rights treaty interpretation and sets out its relevant standards. Drawing from the International Law Commission’s work on ‘Subsequent agreements and subsequent practice in relation to interpretation of treaties’, the author argues that the Vienna rules provide a useful point of departure without the need for additional means of interpretation. This matrix allows sufficient flexibility to accommodate the specific nature of human rights law. The author proposes a normative scale, which can guide the Court in enhancing its methodological consistency. Pursuant to this scale, exigencies for the density of subsequent practice and the degree of acceptance pursuant to Article 38(1)(b) VCLT vary depending on the nature of the rule and the claimed normative value of State practice. Once State practice meets the required standard, it can sustain the legitimacy of treaty interpretation and serve as a catalyst for the advancement of human rights.
The Three Traditional Approaches to Treaty Interpretation: A Current Application to the European Court of Human Rights