Short answers, pulled from the story.
Under the declarative theory codified in the 1933 Montevideo Convention, a sovereign state must have a defined territory, a permanent population, a government, and the capacity to enter into relations with other states. The government must be able to exercise effective control over its territory and population and guarantee the protection of basic human rights.
Westphalian sovereignty is the principle that a nation-state's authority is grounded in its territory and that external powers have no legitimate role in its domestic affairs. It began with the Peace of Westphalia in 1648, which also recognized the right of rulers to determine the religious affiliation of their kingdoms.
Constitutive theory holds that a state becomes a legal person in international law only when recognized by at least one other sovereign state, a position stated by L. F. L. Oppenheim in 1912. Declarative theory, expressed in the 1933 Montevideo Convention, holds that statehood arises from meeting objective criteria of territory, population, government, and capacity for international relations, independent of recognition.
The Turkish Republic of Northern Cyprus is recognized only by Turkey. The international community withheld recognition because international law treats the territory as part of Cyprus. Despite this, the European Court of Human Rights ruled on the 2nd of July 2013 that a de facto recognition of its acts may be necessary for practical purposes.
A de facto state controls a territory and population but lacks international recognition. Somaliland is the most commonly cited contemporary example. Following the Soviet and Yugoslav collapses, several such entities emerged, including Abkhazia, Transdniester, South Ossetia, and the NKR, which persisted for decades without recognition.
Political scientist Peter Katzenstein applied the term semi-sovereign to West Germany in his 1987 book Policy and Politics in West Germany: The Growth of a Semi-sovereign State. He argued that West Germany's sovereignty was constrained internally by its federal system and civil society, and externally by its membership in the European Community and dependence on the United States and NATO for national security.