‘Secession’ is best understood as a process. It culminates when one geographic part of a sovereign state itself becomes a state with full sovereign powers. To do this, the government of the seceding state must exercise effective control over the territory it claims, and it must be recognized as the legitimate authority by other states in the international system.
Secessions are momentous events, as are attempted secessions. The international law governing them is not very clear, and each case is unique. However, it is generally accepted that only ‘peoples’ incapable of exercising their right of self-determination, because of oppression, have a legitimate claim for secession. Normally secessions are driven by groups within a state that are distinct from the rest of the population in terms of religion, ethnicity, and/or language; only such differences seem capable of generating the unity needed to attempt a risky secession. Most secessions are contested by the existing authorities. The usual result is civil war (as in the case of the United States, Eritrea-Ethiopia, Nigeria, and many other examples), and this is often preceded by guerrilla warfare undertaken by radical secessionists and by repression on the part of the central authorities (as in East Timor, Sri Lanka, and Chechnya). Peaceful secessions are very rare. They have occurred when central states have essentially collapsed (as with the USSR) or when federations were dualistic, so that two populations could readily dissolve their common institutions (as in the former Czechoslovakia and in the case of Norway and Sweden). In Canada, the Supreme Court of Canada has ruled that the secession of Quebec – or any other province – can occur, as long as negotiators respect the basic constitutional principles of federalism, democracy, constitutionalism and the rule of law, and the protection of minorities.