Humanitarian intervention in the context of "Use of force in international law"

The Westphalian system, also known as Westphalian sovereignty, is a principle in international law that each state has exclusive sovereignty over its territory. The principle developed in Europe after the Peace of Westphalia in 1648, based on the state theory of Jean Bodin and the natural law teachings of Hugo Grotius. It underlies the modern international system of sovereign states and is enshrined in the United Nations Charter, which states that "nothing ... shall authorize the United Nations to intervene in matters which are essentially within the domestic jurisdiction of any state."

According to the principle, every state, no matter how large or small, has an equal right to sovereignty. Political scientists have traced the concept to the eponymous peace treaties that ended the Thirty Years' War (1618–1648) and Eighty Years' War (1568–1648). The principle of non-interference was further developed in the 18th century. The Westphalian system reached its peak in the 19th and 20th centuries, but has faced recent challenges from advocates of humanitarian intervention.

The North Atlantic Treaty Organization (NATO) carried out an aerial bombing campaign against the Federal Republic of Yugoslavia during the Kosovo War. The air strikes lasted from 24 March 1999 to 10 June 1999. The bombings continued until an agreement was reached that led to the withdrawal of the Yugoslav Army from Kosovo, and the establishment of the United Nations Interim Administration Mission in Kosovo, a UN peacekeeping mission in Kosovo. The official NATO operation code name was Operation Allied Force (Serbian: Савезничка сила / Saveznička sila) whereas the United States called it Operation Noble Anvil (Serbian: Племенити наковањ / Plemeniti nakovanj); in Yugoslavia, the operation was incorrectly called Merciful Angel (Serbian: Милосрдни анђео / Milosrdni anđeo), possibly as a result of a misunderstanding or mistranslation.

NATO's intervention was prompted by Yugoslavia's bloodshed and ethnic cleansing of Kosovar Albanians, which drove the Albanians into neighbouring countries and had the potential to destabilize the region. Yugoslavia's actions had already provoked condemnation by international organisations and agencies such as the UN, NATO, and various INGOs. Yugoslavia's refusal to sign the Rambouillet Accords was initially offered as justification for NATO's use of force. Because Russia and China could use their veto within the Security Council to not authorize an external intervention, NATO launched its campaign without the UN's approval, stating that it was inter alia a humanitarian intervention. The UN Charter prohibits the use of force except in the case of a decision by the Security Council under Article 42, under Article 51 or under Article 53. Three days after the commencement of hostilities, on 26 March 1999, the Security Council rejected the demand of Russia, Belarus and India for the cessation of the use of force against Yugoslavia.

Territorial integrity is the principle under international law where sovereign states have a right to defend their borders and all territory in them from another state. It is enshrined in Article 2(4) of the UN Charter and has been recognized as customary international law. Under this principle, forcible imposition of a border change is an act of aggression.

In the post-World War years, there has been tension between this principle and the concept of humanitarian intervention under Article 73.b of the United Nations Charter "to develop self-government, to take due account of the political aspirations of the peoples, and to assist them in the progressive development of their free political institutions, according to the particular circumstances of each territory and its peoples and their varying stages of advancement."