Political Science International Law
MJ Peterson
  • LAST REVIEWED: 02 April 2019
  • LAST MODIFIED: 30 October 2019
  • DOI: 10.1093/obo/9780199756223-0076


International law can be defined as the substantive norms and rules and related procedural codes that govern relations among states, and the conduct of transactions and relationships across national borders. It is one of the fundamental institutions of the international system, simultaneously reaffirming the organization of the world into autonomous states and providing their governments and other international actors with a set of publicly expressed common standards of conduct and procedures, organizing the provision of governance for an increasingly interconnected world. Initially addressing only relations among sovereign (independent) states, its reach expanded during the period 1860–2000 to include interactions of states with intergovernmental organizations and humans (as peoples, ethnic, racial, religious, or indigenous groups, or as individuals) and state regulation of human conduct within the natural environment. Two broad debates in legal philosophy—one focused on whether the term “law” should be defined as a body or rules or as the set of interactions through which rules are made, amended, and applied; and the other on whether “law” denotes commands backed by centralized force or social norms treated as obligatory for all members of a society—continue to influence how scholars approach international law, as will be elaborated in later sections. Given the continuing decentralization of global-level governance, it appears more useful to use the term “international law” to denote a body of rules, procedures, and related doctrines for interpreting them, and the term “international legal system” to denote two sets of related activity, the highly political processes of making, amending, and occasionally discarding rules, and the more rule-bound processes of applying the existing rules to behavior and using them to resolve particular disputes. Though the political and the legal sometimes intertwine, distinguishing between the two helps make sense of the expansion of the rules to cover more issue areas and the expansion of rule-making to include not only the non-Western states returning to independence after European colonial domination but also the activities of nonstate actors. Distinguishing between law and politics also highlights the effects of legal rules as they encourage some possible courses of action while discouraging others. Thus the study of international law today involves three distinct activities: (1) understanding international law as a distinct legal system; (2) understanding the potentials and limits of using it as a technique for organizing and conducting governance; and (3) drawing on it as an intellectual resource for advancing political, economic, social, and moral goals.


Law schools introduce students to international law through textbooks (sometimes called “treatises”) or casebooks. Textbooks offer general definitions and histories of international law, summarize the body of current rules, and outline the processes of law-making and law-application. Casebooks offer headnotes and brief commentaries guiding readers through excerpts of treaties, international or national court decisions, significant government statements, and resolutions of major intergovernmental organizations. Casebooks are more prevalent in the common law countries (United States, United Kingdom, the Commonwealth) than in other parts of the world. Though the casebooks provide clear connecting threads and an appreciation of the variety of legally relevant documentation, this article emphasizes textbooks because readers beginning the study of international law outside a law school will find them easier to understand. Crawford 2019 and Shaw 2017 provide overviews based mainly on British and Commonwealth practice. Wouters, et al. 2018; Dupuy and Kerbrat 2018; and Stein, et al. 2017 reflect western European traditions, while Murphy 2018 reflects a US perspective. No textbook can be comprehensive in coverage, and the better authors admit this clearly in providing citations to reliable Internet resources, more specialized studies, and the particular judicial decisions or government statements they discuss.

  • Crawford, James. Brownlie’s Principles of Public International Law. 9th ed. Oxford: Oxford University Press, 2019.

    DOI: 10.1093/he/9780199699698.001.0001Save Citation »Export Citation » Share Citation »

    Strongest on legal persons, jurisdiction, rights and responsibilities of states, and on the relation of international and national law; provides little coverage of international environmental and international economic law. Particular emphasis on British and Commonwealth practice.

  • Dupuy, Pierre-Marie, and Yann Kerbrat. Droit international public. 14th ed. Paris: Dalloz, 2018.

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    The leading French textbook, continuing the strong focus on processes of making and applying international law.

  • Murphy, Sean D. Principles of International Law. 3d ed. Minneapolis: West Academic, 2018.

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    Strongest on the relation of international and national law, and on the processes of making and applying law. Provides extended discussion of US practice for incorporating international law in national law and is particularly helpful for understanding the complex legal and political roots of the state practice of the United States.

  • Shaw, Malcolm N. International Law. 8th ed. Cambridge, UK: Cambridge University Press, 2017.

    DOI: 10.1017/CBO9780511841637Save Citation »Export Citation » Share Citation »

    Strongest on legal persons, dispute settlement processes, jurisdiction, rights and responsibilities of states; human rights and international criminal law, relation of international and national law; provides little coverage of international economic law. Most examples are from British, Commonwealth, and US practice.

  • Stein, Torsten, Christian von Buttlar, and Markus Kotzur. Völkerrecht. 14th ed. Munich: F. Vahlen, 2017.

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    Introductory textbook introducing the main branches of public international law as practiced at the global and European Union levels with an emphasis on the relation between political events and legal interpretation.

  • Wouters, Jan, Cedric Ryngaert, Tom Ruys, and Geert De Baere. International Law: A European Perspective. Oxford: Hart, 2018.

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    Introductory textbook developed for use in European university courses on public international law taught in English. It includes extensive coverage of European Union and Council of Europe institutions, and the three-sided interplay among general international law, European regional law, and national law of EU member states.

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