Tackling Lacunae in International Courts and Tribunals’ Procedure: The Role of External Precedentf

International courts and tribunals are frequently faced with the need to fill lacunae in their own rules of procedure. Among the many tools at the disposal of adjudicative bodies, external precedent emerges as one of the most flexible and intuitive, allowing to “borrow” from the procedure of other bodies. This paper offers an overview of how international courts and tribunals use external precedent on procedural matters in the context of a number of typical gap-filling techniques. To this end, it delves into the possibility of employing external precedent as a subsidiary means for the determination of rules of law, as an instrument for carrying out systemic interpretation, and as a way of invoking and delimiting inherent powers. Through this analysis, the paper questions the view according to which recourse to external precedent necessarily contributes to the legitimacy of international courts and tribunals. It shows that, at least in procedural matters, this nexus is not straightforward and varies according to the context in which reference to external precedent is made.