The development of International Law is one of the primary goals of the United Nations. The Charter of the United Nations, in its Preamble, sets the objective "to establish conditions under which justice and respect for the obligations arising from treaties and other sources of international law can be maintained".

International Law defines the legal responsibilities of States in their conduct with each other, and their treatment of individuals within State boundaries. Its domain encompasses a wide range of issues of international concern such as human rights, disarmament, international crime, refugees, migration, problems of nationality, the treatment of prisoners, the use of force, and the conduct of war, among others. It also regulates the global commons, such as the environment, sustainable development, international waters, outer space, global communications and world trade.

Over the years, the United Nations has sponsored over 500 multilateral agreements, which address a broad range of common concerns among states and are legally binding for the countries that ratify them.

To become party to a treaty, a State must express, through a concrete act, its willingness to undertake the legal rights and obligations contained in the treaty - it must "consent to be bound" by the treaty. This is usually accomplished through signature and ratification of the treaty, or if it's already in force, by accession to it.

Each year, the UN holds a Treaty Event, highlighting a group of treaties, as a way to encourage Member States to sign, ratify or otherwise support these treaties.

Different treaties may create different treaty body regimes to encourage the parties to abide by their obligations and undertake actions required for compliance.

Legal disputes between states can be referred to the International Court of Justice, the principal judicial organ of the United Nations, which also gives advisory opinions on legal questions referred to it by duly authorized international organs and agencies.

The international community has long aspired to create a permanent international court to try the most serious international crimes, and, in the 20th century, it reached consensus on definitions of genocide, crimes against humanity and war crimes. The Nuremberg and Tokyo trials addressed war crimes, crimes against peace, and crimes against humanity committed during the Second World War.

In the 1990s, after the end of the Cold War, tribunals such as the International Criminal Tribunals for the former Yugoslavia (ICTY) and for Rwanda (ICTR) were established to fight impunity by trying crimes committed within a specific time-frame and during a specific conflict.

In 1998, the international community reached an historic milestone when 120 States adopted the Rome Statute, the legal basis for establishing the permanent International Criminal Court (ICC).

The ICC is an independent international organization, and is not part of the United Nations system. Its seat is at The Hague in the Netherlands.

Cases are referred to the Court by states parties, by the UN Security Council or on the initiative of the Court's Prosecutor.