quality:correction, quality:corruption
By fiction or fiat

Power can come from force, but formal legitimacy is often established, even if only by fictitious claims of continuity (e.g., a forged claim of descent from a previous dynasty). There have been cases of sovereignty granted by deliberate act, even when accompanied by orders of succession (as may be the case in a dynastic split). Such grants of sovereignty are usually forced, as is common with self-determination granted after nationalist revolts. This occurred with the last Attalid king of Hellenistic Pergamon, who by testament left his realm to Rome to avoid a disastrous conquest.