This paper is prepared for UNCTAD’s initiative on responsible sovereign lending and borrowing. It surveys the fragmented legal landscape of sovereign debt, the onset of treaty and custom fatigue in the wake of contentious debates about sovereign bankruptcy and Odious Debt, and the peculiar form of soft law in the field. Against this background, the Principles are unusual for their ambition and comprehensive reach: they aspire to govern debtors and creditors, rich and poor countries, official and private actors, domestic and external debt. The Principles are also unusual for having mobilized diverse stakeholders among borrowers, lenders and NGOs in the drafting process. I draw on studies in soft law and new governance to recommend concrete strategies for implementing the Principles. I argue against spending political capital on turning them into a treaty, which would take years to negotiate and yield weaker substantive commitments. Informed by recent experience with best practices in international finance — including project finance, extraction revenue management, foreign aid, sovereign investment, and emerging market bonds — a strategy for implementing UNCTAD Principles should strive to embed compliance in multi-stakeholder arrangements for ongoing disclosure, assessment, interpretation, and adaptation [...]