Short answers, pulled from the story.
A sovereign state is a legal fiction that exists as a quasi-abstract object distinct from its territory and people, possessing the highest authority over a territory to command armies, collect taxes, and sign treaties. This entity occupies a unique ontological category that allows it to persist even when its physical territory is occupied, as seen during the Second World War when governments-in-exile maintained diplomatic relations with the Allies.
The modern concept of the sovereign state was forged in the fires of religious war and political chaos, culminating in the Peace of Westphalia on the 28th of October 1648. This treaty established a new international system based on territoriality and the absolute absence of external interference in domestic structures, creating what is now known as Westphalian sovereignty.
The 1933 Montevideo Convention defines a state as a person in international law if it meets four criteria: a defined territory, a permanent population, a government, and the capacity to enter into relations with other states. According to this declarative theory, an entity's statehood is independent of its recognition by other states, as long as the sovereignty was not gained by military force.
Entities such as Northern Cyprus and Rhodesia exist in a state of legal limbo, exercising de facto control over a territory but lacking international recognition. The Turkish Republic of Northern Cyprus has been withheld recognition by almost the entire international community, with only Turkey recognizing it, while Rhodesia was widely recognized only by South Africa.
Before 1900, sovereign states enjoyed complete immunity from prosecution in foreign courts, but countries including Australia, Canada, Singapore, South Africa, Pakistan, and the United States have introduced restrictive immunity by statute. This legal shift explicitly limits jurisdictional immunity to public acts, but not private or commercial ones, reflecting a global order where the state must be held accountable for its actions.
A semi-sovereign state is an entity that is officially acknowledged as sovereign but whose theoretical sovereignty is significantly impaired in practice, such as Belarus in its relationship with Russia. Political scientist Peter Katzenstein famously applied the term to West Germany in his 1987 book Policy and Politics in West Germany: The Growth of a Semi-sovereign State to describe limitations from both internal federal systems and external alliances.