International legal theory, or theories of international law, comprise a variety of theoretical and methodological approaches used to explain and analyse the content, formation and effectiveness of international law and institutions and to suggest improvements. Some approaches center on the question of compliance: why states follow international norms in the absence of a coercive power that ensures compliance. Other approaches focus on the problem of the formation of international rules: why states voluntarily adopt international legal norms, that limit their freedom of action, in the absence of a world legislature (centralized legislature, court with compulsory jurisdiction, or an executive with enforcement powers). Other perspectives are policy oriented; they elaborate theoretical frameworks and instruments to criticize the existing rules and make suggestions on how to improve them. Some of these approaches are based on domestic legal theory, others are interdisciplinary, while others have been developed expressly to analyse international law.
Classical approaches to international law International law in ancient Rome The idea of international law in Roman times is a complicated one. For, not only does the Roman Republic and following empire itself dominate a long period of time in history, but also the very debate over whether or not the term "international law" is an applicable term is not yet decided.Lesaffer, Randall. "Argument from Roman Law in Current International Law: Occupation and Acquisitive Prescription" Volume 16, Number 1 (European Journal of International Law 2005). Many scholars and authors define international law as "the law governing relations between sovereign, territorial states."Lesaffer (2005), 25–58. Any attempt to find a similar parallel in Roman law would find a logical starting point in the ius gentium (the laws of nations).Mousourakis, George "The Historical and Institutional Context of Roman Law" (Ashgate Publishing Company, 2003), 22. The ius gentium began as a Roman recognition of like legal practices and institutions (such as slavery) that was found at that time in most states.Mousourakis (2003), 23. This brand of law was in fact private law in itself and mainly dictated the way in which the Roman state was to deal with individual foreigners, not entire states. However, when citizenship was granted to all free men in the empire in 212 A.D. ius gentium ceased to cling to its original definition and instead was applied to states as a whole. Some semblance of modern international law can therefore be found in this shift. The actual extent of these origins and their relevance to modern law is a topic that has not yet been approached in any depth. Natural law Many early international legal theorists were concerned with axiomatic truths thought to be reposed in natural law. Sixteenth century natural law writer, Francisco de Vitoria, a professor of theology at the University of Salamanca, examined the questions of the just war, the Spanish authority in the Americas, and the rights of the Native American people.
Eclectic or Grotian approach Hugo Grotius, a Dutch theologian, humanist and jurist played a key role in the development of modern international law. In his De jure Belli ac Pacis Libri Tres ("Three Books on the Law of War and Peace") of 1625, and drawing from the Bible and from St. Augustine's just war theory, he argued that nations as well as persons ought to be governed by universal principles based on morality and divine justice. Drawing, though, from domestic contract law, he argued that relations among polities ought to be governed by the law of peoples, the jus gentium, established by the consent of the community of nations on the basis of the principle of pacta sunt servanda, that is, on the basis of the observance of commitments. On his part, Christian von Wolff, contended the international community should be a world superstate (civitas maxima), having authority over the component member states. Emmerich de Vattel rejected this view and argued instead for the equality of states as articulated by 18th century natural law. In Le droit des gens, de Vattel suggested that the law of nations was composed of custom and law on the one hand, and natural law on the other.
During the seventeenth century, the basic tenets of the Grotian or eclectic school, especially the doctrines of legal equality, territorial sovereignty, and independence of states, became the fundamental principles of the European political and legal system and were enshrined in the 1648 Peace of Westphalia.
Legal positivism The early positivist school emphasized the importance of custom and treaties as sources of international law. Early positivist scholar Alberico Gentili used historical examples to posit that positive law (jus voluntarium) was determined by general consent. Another positivist scholar, Richard Zouche, published the first manual of international law in 1650.
Legal positivism became the dominant legal theory of 18th century and found its way into international legal philosophy. At the time, Cornelius van Bynkershoek asserted that the bases of international law were customs and treaties commonly consented to by various states. John Jacob Moser emphasized the importance of state practice in international law. Georg Friedrich von Martens published the first systematic manual on positive international law, Precis du droit des gens moderne de l'Europe. During the 19th century, positivist legal theory became even more dominant due to nationalism and the Hegelian philosophy. International commercial law became a branch of domestic law: private international law, separate from public international law. Positivism narrowed the range of international practice that might qualify as law, favouring "rationality" over "morality" and "ethics". The 1815 Congress of Vienna marked the formal recognition of the political and international legal system based on the conditions of Europe.
Modern legal positivists consider international law as a unified system of rules that emanates from the states' will. International law, as it is, is an "objective" reality that must be distinguished from law "as it should be." Classic positivism demands rigorous tests for legal validity. Extralegal arguments (i.e., arguments that have no textual, systemic or historical basis on the law) are deemed irrelevant to legal analysis. There is only hard law, no soft law.Bruno Simma and Andreas L. Paulus "Symposium on method in International Law: The Responsibility of Individuals for Human Rights Abuses in Internal Conflicts: A Positivist View" 93 American Journal of International Law 302 (April, 1999). Criticisms of positivist international legal theory include its rigidity, its focus on state consent, without allowing for interpretation, and the fact that it does not allow moral judgements regarding a State's conduct as long as it follows international norms.
International relations – international law approaches
Legal scholars have drawn from the four main schools of thought in the areas of political science and international relations: realism, liberalism, institutionalism, and constructivism to examine, through an interdisciplinary approach, the content of legal rules and institutions, to explain why and how international law and legal institutions came to be and why they are effective.Abbot, Kenneth W. "Symposium on Method in International Law: International Relations Theory, International Law and the Regime Governing Atrocities in Internal Conflicts." (1999): 361–378. These methods have led some scholars to reconceptualize international law in general.Anne-Marie Slaughter; Andre S. Tulumello; Stepan Wood, International Law and International Relations Theory: A New Generation of Interdisciplinary Scholarship, 92 American Journal of International Law 367–397 (1998) at p. 369: "We identify three ways that lawyers are using materials and insights from IR theory: to diagnose substantive problems and frame better legal solutions; to explain the structure or function of particular international legal rules or institutions; reconceptualize or reframe particular institutions or international law generally."
Realism Realism contends that, in an anarchic international system, states' main objective is for survival that obligates them to maximize their relative power in order to preserve their territory and existence. Since international cooperation is possible only inasmuch as it responds to the states' self-interest in maximizing their power and prospects for survival, states do not pursue cooperation on the basis of normative commitments.Hans J. Morgenthau, Positivism, Functionalism, and International Law, 34 American Journal of International Law 260 (1940). According to Realist legal scholars, states adopt only international legal norms that either enhance their power, formalize the subordination of weaker states, or that they intend to violate deliberately to their own advantage.William C. Bradford, In The Minds of Men: A Theory of Compliance with the Laws of War (2004) p. 7. International Law may thus address only peripheral matters that do not impact the states' power or autonomy. Consequently, for realists, international law is a "tenuous net of breakable obligations."Stanley Hoffmann, Conditions of World Order 364 (1956).
Within the Realist approach, some scholars have proposed an "enforcement theory" according to which international legal norms are effective insofar as they "publicize clear rules, enhance monitoring of compliance, and institutionalize collective procedures for punishing violations, thereby enhancing the deterrent and coercive effects of a stable balance of power."William C. Bradford, In The Minds of Men: A Theory of Compliance with the Laws of War (2004) p. 8. Thus, the role of reciprocity and sanctions is underlined. Morrow, for instance, notes that:
Liberalism Based on the liberal international relations theory, some scholars argue that the states' stance towards international law is determined by their domestic politics and, in particular, by the aggregation of the preferences of key domestic individuals and groups toward the rule of law. Thus, democratic states, having a representative government, are more likely than non-democratic states to accept the legal regulation of both domestic and international politics, and more likely to accept and observe international law. Furthermore, democratic societies are linked by a complex net of interstate, transnational and transgovernmental relations so that both their foreign policy bureaucracies and their civil societies are interested in promoting and strengthening transnational cooperation through the creation and observance of international legal norms.William C. Bradford, In The Minds of Men: A Theory of Compliance with the Laws of War (2004) p. 9. Hence, the adoption of and the compliance with international legal norms among democratic states should be easier and more peaceful than the observance of international law among non-democratic states. In this regard, Anne-Marie Slaughter notes that:
Rational choice and game theory This approach to law applies theories of economics to identify the legal implications of maximizing behavior inside and outside of markets. Economics is the study of rational choice under limited conditions.Hawley, Frederick Barnard. "The Definition of Economics".The American Economic Review, Vol. 3, No. 3. (September 1913), 606–609. Rational choice is the assumption that individual actors seek to maximize their preferences.Hawley 1913, 606–609.