This chapter examines from a comparative perspective the national legal regimes that govern treaty-making and treaty withdrawal, functions that in many countries were traditionally vested in the executive. Drawing from an original dataset that covers 101 countries for the period 1815-2013, the chapter identifies several large-scale trends. First, it confirms a sustained trend towards greater parliamentary involvement in treaty-making. Second, it shows that many countries recognize executive agreements and other alternative procedures through which the executive can conclude internationally binding agreements without parliamentary approval, but that these “work-arounds” are typically subject to significant constraints affecting the executive’s discretion and the domestic legal status of the resulting agreements. Third, it shows that in recent years several countries have introduced constraints on the executive’s ability to withdraw from treaties without parliamentary approval. Finally, it draws attention to the little-noticed role of national judiciaries in treaty-making, by showing that in many legal systems treaties are subject to constitutional review prior to ratification. The chapter discusses the implications of these four trends, all of which represent moves away from the executive-dominated world of traditional treaty relations. It hypothesizes that these trends respond to growing separation of powers concerns as treaties increasingly shape domestic law. 

Pierre-Hugues Verdier & Mila Versteeg, Separation of Powers, Treaty-Making, and Treaty Withdrawal: A Global Survey, in Oxford Handbook of Comparative Foreign Relations Law, Oxford University Press, 135–155 (2019).