Sovereign right

State sovereignty, or Westphalian sovereignty, is the principle of international law that each nation-state has sovereignty over its territory and domestic affairs, to the exclusion of all external powers, on the principle of non-interference in another country's domestic affairs, and that each state (no matter how large or small) is equal in international law. After European influence spread across the globe, these principles became ideals central to international law.

The principle of sovereignty thus underlies the modern international system of states. The origins of this system are often traced in scholarly and popular literature to the Peace of Westphalia, signed in 1648, which ended the Thirty Years' War.

The traditional view of the Westphalian system is that the Peace of Westphalia was an agreement to respect the principle of territorial integrity. In the Westphalian system, the national interests and goals of states (and later nation-states) were widely assumed to go beyond those of any citizen or any ruler. States became the primary institutional agents in an interstate system of relations. The Peace of Westphalia is said to have ended attempts to impose supranational authority on European states. The "Westphalian" doctrine of states as independent agents was bolstered by the rise in 19th century thought of nationalism, under which legitimate states were assumed to correspond to nations—groups of people united by language and culture.

The Westphalian system reached its peak in the late 19th century. Although practical considerations still led powerful states to seek to influence the affairs of others, forcible intervention by one country in the domestic affairs of another was less frequent between 1850 and 1900 than in most previous and subsequent periods.

The Peace of Westphalia is important in modern international relations theory, and is often defined as the beginning of the international system with which the discipline deals. However, recent scholarship suggests that the Westphalian treaties actually had little to do with the principles – i.e., sovereignty, non-intervention, and the legal equality of states – with which the treaties are often associated. For example, Osiander writes that "[t]he treaties confirm neither [France's or Sweden's] "sovereignty" nor anybody else's; least of all do they contain anything about sovereignty as a principle."

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