trade. with the understanding that an informal treatment is all that the existing literature has to offer on many of them Sections 2 and 3 of the chapter provide legal background on the field of international law, followed by a discussion of general economic considerations that cut across a range of possible topics. The analysis will encompass the various possible functions of international law, the challenges involved in realizing gains from international cooperation, the design and function of mechanisms for its enforcement, and the interface between domestic and international law. Sections 4-10 of the chapter consider particular topics, including strategic alliances and laws of war, international rade. international investment international antitrust. human rights law. conflicts of law and the international commons(fisheries) As a final, preliminary disclaimer, I have not undertaken to survey and incorporate the vast political science literature on public international law. Much of that literature is excellent, and the"rational choice literature in particular is often quite close in both spirit and method to the work of economists. I omit attention to it not because of any negative judgment about its quality, but to make the task at hand a manageable one Readers seeking a window into the rational choice perspective on international relations and institutions might wish to consult Snidal (1996)and(2002). Carlsnaes, Risse and Simmons(2002) provide a broader introduction to modern international relations work in political science 2. Legal background The field of international law is conventionally divided into two subfields: public"international law and"privateinternational law. "Public"international law refers to the body of law that governs relations between states or countries. " Private international law refers to the body of law that governs international relations between private citizens or companies. Most private international law relates to international b s transactions, and may be subsumed for analytic purposes under other topics such as contract law, corporate law and tax law that are the subject of other chapters the Handbook of Law and Economics. Accordingly, my focus in this chapter is almost exclusively on public international law. The genesis of public international law necessarily differs from that of domestic law. No international legislature exists to pass the equivalent of domestic statutes, and no international court exists with the power to create a general international common law Instead, public international law arises only by agreement among statestrade, with the understanding that an informal treatment is all that the existing literature has to offer on many of them. Sections 2 and 3 of the chapter provide legal background on the field of international law, followed by a discussion of general economic considerations that cut across a range of possible topics. The analysis will encompass the various possible functions of international law, the challenges involved in realizing gains from international cooperation, the design and function of mechanisms for its enforcement, and the interface between domestic and international law. Sections 4-10 of the chapter consider particular topics, including strategic alliances and laws of war, international trade, international investment, international antitrust, human rights law, conflicts of law, and the international commons (fisheries). As a final, preliminary disclaimer, I have not undertaken to survey and incorporate the vast political science literature on public international law. Much of that literature is excellent, and the “rational choice” literature in particular is often quite close in both spirit and method to the work of economists. I omit attention to it not because of any negative judgment about its quality, but to make the task at hand a manageable one. Readers seeking a window into the rational choice perspective on international relations and institutions might wish to consult Snidal (1996) and (2002). Carlsnaes, Risse and Simmons (2002) provide a broader introduction to modern international relations work in political science. 2. Legal Background The field of international law is conventionally divided into two subfields: “public” international law and “private” international law. “Public” international law refers to the body of law that governs relations between states or countries. “Private” international law refers to the body of law that governs international relations between private citizens or companies. Most private international law relates to international business transactions, and may be subsumed for analytic purposes under other topics such as contract law, corporate law and tax law that are the subject of other chapters in the Handbook of Law and Economics. Accordingly, my focus in this chapter is almost exclusively on public international law. The genesis of public international law necessarily differs from that of domestic law. No international legislature exists to pass the equivalent of domestic statutes, and no international court exists with the power to create a general international common law. Instead, public international law arises only by agreement among states