Due Diligence in International Law: A Useful Renaissance or 'All Things to All People'?

Abstract Few concepts have become as prominent in recent international law publications as ‘due diligence’. Still, its nature and content remain notably ambiguous. This essay reflects on the main takeaways from recent scholarly debates on due diligence. These takeaways are presented as five propositions that seek to capture the common findings or areas of agreement in the scholarship under review, having regard to the existing case law of international courts and tribunals. These propositions are intended to inform our understanding of the nature, content and scope of application of due diligence and are, in principle, agnostic as to the particular field of international law. With an eye to the future, this essay has also singled out certain areas in the debate where scholars disagree or where the law may not yet be settled. Those areas may benefit from further research, practice of states, clarification by international courts and tribunals and, likely, codification by the International Law Commission in the near future. These efforts will go a long way towards ensuring that due diligence remains a well-circumscribed concept and thus useful to states and other participants in the international legal order.