The right of a people to self-determination is a cardinal principle in modern international law (commonly regarded as a jus cogens rule), binding, as such, on the United Nations as authoritative interpretation of the Charter's norms. It states that peoples, based on respect for the principle of equal rights and fair equality of opportunity, have the right to freely choose their sovereignty and international political status with no interference.

Mollucan Protesters against the treatment of Suharto's government to East Timor, in The Hague, Netherlands, 1986.

The concept was first expressed in the 1860s, and spread rapidly thereafter.[5][6] During and after World War I, the principle was encouraged by both Soviet Premier Vladimir Lenin and United States President Woodrow Wilson. Having announced his Fourteen Points on 8 January 1918, on 11 February 1918 Wilson stated: "National aspirations must be respected; people may now be dominated and governed only by their own consent. 'Self determination' is not a mere phrase; it is an imperative principle of action."

During World War II, the principle was included in the Atlantic Charter, declared on 14 August 1941, by Franklin D. Roosevelt, President of the United States, and Winston Churchill, Prime Minister of the United Kingdom, who pledged The Eight Principal points of the Charter.[8] It was recognized as an international legal right after it was explicitly listed as a right in the UN Charter.[9] The principle does not state how the decision is to be made, nor what the outcome should be, whether it be independence, federation, protection, some form of autonomy or full assimilation. Neither does it state what the delimitation between peoples should be—nor what constitutes a people. There are conflicting definitions and legal criteria for determining which groups may legitimately claim the right to self-determination. Broadly speaking, the term self-determination also refers to the free choice of one's own acts without external compulsion.

Defining "peoples"

There is not yet a recognized legal definition of "peoples" in international law. Vita Gudeleviciute of Vytautas Magnus University Law School, reviewing international law and UN resolutions, finds in cases of non-self-governing peoples (colonized and/or indigenous) and foreign military occupation "a people" is the entire population of the occupied territorial unit, no matter their other differences. In cases where people lack representation by a state's government, the unrepresented become a separate people. Present international law does not recognize ethnic and other minorities as separate peoples, with the notable exception of cases in which such groups are systematically disenfranchised by the government of the state they live in. Other definitions offered are "peoples" being self-evident (from ethnicity, language, history, etc.), or defined by "ties of mutual affection or sentiment", i.e. "loyalty", or by mutual obligations among peoples. Or the definition may be simply that a people is a group of individuals who unanimously choose a separate state. If the "people" are unanimous in their desire for self-determination, it strengthens their claim. For example, the populations of federal units of the Yugoslav federation were considered a people in the breakup of Yugoslavia, although some of those units had very diverse populations. Another example are the Macedonians in Macedonia. Bulgaria and Greece are now arguing against the Macedonians’ right to self-determination under international law. Many of the Macedonians who live in the region have ancestors that date thousands of years and they have the right to identify as Macedonians. Although there is no fully accepted definition of peoples, references are often made to a definition proposed by UN Special Rapporteur Martínez Cobo in his study on discrimination against indigenous populations. UN Independent Expert on the Promotion of a democratic and equitable International Order, Alfred de Zayas, relied on the "Kirby definition" in his 2014 Report to the General Assembly A/69/272 as "a group of persons with a common historical tradition, racial or ethnic identity, cultural homogeneity, linguistic unity, religious or ideological affinity, territorial connection, or common economic life. To this should be added a subjective element: the will to be identified as a people and the consciousness of being a people."

Abulof suggests that self-determination entails the "moral double helix" of duality (personal right to align with a people, and the people's right to determine their politics) and mutuality (the right is as much the other's as the self's). Thus, self-determination grants individuals the right to form "a people," which then has the right to establish an independent state, as long as they grant the same to all other individuals and peoples.

Criteria for the definition of "people having the right of self-determination" was proposed during 2010 Kosovo case decision of the International Court of Justice:

Self-determination versus territorial integrity

Celebration of the Declaration of Independence of Kosovo in 2008

National self-determination appears to challenge the principle of territorial integrity (or sovereignty) of states as it is the will of the people that makes a state legitimate. This implies a people should be free to choose their own state and its territorial boundaries. However, there are far more self-identified nations than there are existing states and there is no legal process to redraw state boundaries according to the will of these peoples. According to the Helsinki Final Act of 1975, the UN, ICJ and international law experts, there is no contradiction between the principles of self-determination and territorial integrity, with the latter taking precedence.

Donetsk status referendum organized by separatists in Ukraine. A line to enter a polling place, 11 May 2014

Allen Buchanan, author of seven books on self-determination and secession, supports territorial integrity as a moral and legal aspect of constitutional democracy. However, he also advances a "Remedial Rights Only Theory" where a group has "a general right to secede if and only if it has suffered certain injustices, for which secession is the appropriate remedy of last resort." He also would recognize secession if the state grants, or the constitution includes, a right to secede.

Vita Gudeleviciute holds that in cases of non-self-governing peoples and foreign military occupation the principle of self-determination trumps that of territorial integrity. In cases where people lack representation by a state's government, they also may be considered a separate people, but under current law cannot claim the right to self-determination. On the other hand, she finds that secession within a single state is a domestic matter not covered by international law. Thus there are no on what groups may constitute a seceding people.

During the 2019-20 Hong Kong protests, calls rose for self-determination by Hongkongers.

A number of states have laid claim to territories, which they allege were removed from them as a result of colonialism. This is justified by reference to Paragraph 6 of UN Resolution 1514(XV), which states that any attempt "aimed at partial or total disruption of the national unity and the territorial integrity of a country is incompatible with the purposes and principles of the Charter". This, it is claimed, applies to situations where the territorial integrity of a state had been disrupted by colonisation, so that the people of a territory subject to a historic territorial claim are prevented from exercising a right to self-determination. This interpretation is rejected by many states, who argue that Paragraph 2 of UN Resolution 1514(XV) states that "all peoples have the right to self-determination" and Paragraph 6 cannot be used to justify territorial claims. The original purpose of Paragraph 6 was "to ensure that acts of self-determination occur within the established boundaries of colonies, rather than within sub-regions". Further, the use of the word attempt in Paragraph 6 denotes future action and cannot be construed to justify territorial redress for past action. An attempt sponsored by Spain and Argentina to qualify the right to self-determination in cases where there was a territorial dispute was rejected by the UN General Assembly, which re-iterated the right to self-determination was a universal right.