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.
[3] 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.
[4] 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.
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.
Hugo Grotius, a Dutch theologian, humanist and jurist played a key role in the development of modern international law.
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.
At the time, Cornelius van Bynkershoek asserted that the bases of international law were customs and treaties commonly consented to by various states.
Georg Friedrich von Martens published the first systematic manual on positive international law, Precis du droit des gens moderne de l'Europe.
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.
[7] 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.
"[10] 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.
Morrow, for instance, notes that: International politics in modern times generally recognizes no authority above the nation-state.
[14]This approach to law applies theories of economics to identify the legal implications of maximizing behavior inside and outside of markets.
Game theory can demonstrate how actors with maximizing behavior might fail to take action increase join gain.
Unlike the American Legal System, it considers normative values other than democracy, such as "…feminism, republicanism, law and economics, liberalism as well as human rights, peace and protection to the environment.
The New Haven School is a policy-oriented perspective on international law pioneered by Myres S. McDougal, Harold D. Lasswell, and W. Michael Reisman.
[28][29] Its intellectual antecedents lie in sociological jurisprudence of Roscoe Pound and the reformist ambitions of the American Legal Realists.
International law itself reflects the expectations of relevant community members about stable patterns of behavior created by assertions of control by legal authorities.
[32] The method proposes that the nature of international law is limited because it is determined by language, which is biased and still stuck in the conventional structures of politics and power.
Feminist theorists propose to change legal language to make it more inclusive of women, or to rethink law completely, so it is possible to promote broader social goals of justice and equality.
Feminist theorist Hilary Charlesworth criticizes the dialogue of women as victims in need of protection from both men and international law.
While human rights conventions have recently begun to generalize in regard to equality and its recipients, in the past, any discussions of sexual orientation and gender identity have gone largely untouched.
As LGBT theory has become more prominent in scholarly works, international courts and international law organizations (particularly the European Union and the United Nations) have considered workplace discrimination on the basis of sexuality, issues stemming from the definition of family in regard to homosexual unions, the position of transsexuals in the question of sexual orientation, the need for recognition of LGBT rights in regard to general health advocacy and the HIV/AIDS crisis, the inclusion of and LGBT advocacy group within the UN (with advisor status), and the ongoing active persecution of people engaging in homosexual acts, among other issues.
TWAIL scholars try to avoid presenting the "Third World" as a unified, coherent place but rather use the term to indicate peoples who have the shared experience of underdevelopment and marginalization.