After World War II, The Kosovar Albanians, a newly emerging community started making demonstrations in order to secede Kosovo from Socialist Federal Republic of Yugoslavia (SFRY) and make it a part of Albania. After the 1968 demonstrations the leader of SFRY Mr. Josip Broz Tito granted substantial autonomy to Kosovo and its people in 1974 by changing the SFRY Constitution and raising Kosovo's status to autonomous province. After the 1981 demonstration for a new Republic of Kosovo, Yugoslav Military violently quashed the act.
After the disintegration of Socialist Federal Republic of Yugoslavia due to political crisis in the 1980's and the death of their leader Mr. Josip Broz Tito, a new country emerged, a country with a new motive. The leader Milosevic defined a new Federal Republic of Yugoslavia with the Serbian Majority. Even though Milosevic competed to be the legal successor of SFRY but by the virtue of Security Council Resolution 777 it was clearly rejected and was also not allowed membership in the United Nations. Rather than promoting the rights of the Kosovar Albanian Community, Milosevic started curbing them and entered into gross Humanitarian violations. The Kosovar Albanians organized a new force in order to retaliate to Milosevic government known as the Kosovo Liberation Army . This fight between the forces of Kosovo Liberation Army and the Milosevic Government came to end only after the intervention by NATO and the eventual bombing. Finally they came into an agreement at the Ramboullett Conference which intended a peaceful roadmap for Kosovo though not determining its final status. The Rambouillett Accords were not signed by the Serbs but were agreed by the Albanians and Kosovars.
Current Status of Kosovo, The Federal Republic of Yugoslavia
The current status of Kosovo has still been up to question. There have been a lot of countries which have recognized the presence of Kosovo and a lot which have not. When the Declaration of Independence was made for Kosovo, the International Court of Justice passed an advisory opinion proclaiming the declaration to be not illegal by the virtue of general internatational law. Those who want to grant Kosovo statehood often argue that Kosovo deserves statehood as they satisfy the four principles of Montevedio Convention of 1933 used to define statehood which are: 1) A permanent Population 2) A defined territory 3) Government and 4) Capacity to enter into relations with other states as these principles have gone on to become a part of customary international law and may attain the status of jus cogens (peremptory norms) through which derogations are not allowed and they often argue that the Kosovars have a right to self-determination enshrined in Article 1.2 of the United Nations Charter,Declarations of Principles of International Law concerning friendly relations and the International Court of Justice Case Of East Timor in which it was confirmed that right to self determination is of erga omnes character which are basic moral obligations which countries need to follow.As far as Federal Republic of Yugoslavia goes, it broke down after the intervention and bombing of NATO which was held in order to stop the mass human rights violations. Serbia and Montenegro was formed and the union got separated into Serbia and Montenegro as different countries after the referendum of 2006 though Serbia became the official successor of Serbia and Montenegro.
The Intervention: Its legitimacy and its legality.
After the human rights violations conducted against the Kosovars, and since the North Atlantic Treaty Organization failed to have a UN Authorized Intervention acting under Chapter VII of the UN Charter as the Resolution was vetoed over time, they decided to intervene in an unauthorized manner which was considered to be a clear violations of Chapter 1 Article 2.4 of the United Nations Charter which reads as follows:
“All Members shall refrain in their international relations from the threat or use of force against the territorial integrity or political independence of any state, or in any other manner inconsistent with the Purposes of the United Nations.”
And since force was used against a state even though not a member of the United Nations this intervention was considered illegal though morally legitimate.
Though the point which has to be taken into consideration over here is the fact that the article talks about 'use of force against the territorial integritity' of a state. Territorial integrity even though not a part of codified international law and ambiguous may refer to state sovereignty. Since state sovereignty is defined by rule of law maintained by the government in this case since the government did not confront with certain basic universal principles as the Milosevic Government did not recognize the Universal Declaration of Human Rights nor the Geneva Conventions of 1949 which is used to determinate basic International Humanitarian Law, nor did they sign the United Nations Charter, thus by the virtue of Rule According to Higher Law which means that no law may be enforced by the government unless it confirms with certain universal principles of fairness, morality and justice. Thus technically the rule of law or the government law was never into play which is usually used to determine the state sovereignty and thus the intervention might be justified by the virtue of it being taken place in a non-government rule holding state as it might be considered that Milosevic's Government never held rule of law in the first place legally.
Though again since international law is up to interpretation and Milosevic's government might be in alignment with the universal principles according to critics thus this question still remains up to interpretations.
For one thing surely as Kofi Annan the former Secretary-General said 鍍here are times when the use of force may be legitimate in one for one thing sure Kosovo is a Sui Generis case (one of its own kind) and the international community hopes it does not happen again.