Arbitrators as advisors: Evidence from changes in investment treaty design

Abstract The international investment regime is increasingly reliant on the expertise of lawyers. What impact does the rise of lawyers have on the design of international cooperation? We argue that lawyers can advise states to create international investment agreements (IIAs) that lower institutional barriers, making it easier for investors to access legal dispute resolution. Using an original dataset of 479 arbitration practitioners registered with the International Centre for Settlement of Investment Disputes from 1974 to 2023, along with a newly constructed dataset measuring investors’ access to legal dispute settlement, we find that states with a larger pool of arbitration practitioners are more likely to amend their treaties in a way that eases investors’ access to Investor-State Dispute Settlement (ISDS). We also find support for our theory through interviews with arbitration practitioners. Our findings can explain why states maintain investor-friendly ISDS clauses, even after suffering losses from previous ISDS disputes. The growing reliance on lawyers can reshape and professionalize international cooperation beyond the purview of states.