This book presents a comparative analysis of the role of domestic courts in treaty application. In evaluating the role of domestic courts, it is helpful to distinguish among three types of treaty provisions. Horizontal treaty provisions regulate relations between states; vertical provisions regulate relations between states and private parties; and transnational provisions regulate relations among private parties that cut across national boundaries. Domestic courts are rarely invited to apply horizontal treaty provisions. However, private parties frequently seek access to domestic courts to vindicate rights that arise from vertical and/or transnational treaty provisions.

The use of treaties to regulate vertical and transnational relationships is not a new phenomenon. Two centuries ago, Chief Justice Marshall, writing for the U.S. Supreme Court, declared: “Each treaty stipulates something respecting the citizens of the two nations, and gives them rights. Whenever a right grows out of, or is protected by, a treaty, it is sanctioned against all the laws and judicial decisions of the states; and whoever may have this right, it is to be protected.” Although states have used treaties to regulate transnational and vertical relationships for centuries, there has been an exponential growth in treaty making in this area over the past few decades.