What does cuius regiō mean in Latin?

cuius regiō, a proverb, means “The sovereign of a state or territory has the right to determine what religion(s) may be practiced therein.”.

cuius regiō

cuius regiō, eius religiō

GermanyNew LatinThe sovereign of a state or territory has the right to determine what religion(s) may be practiced therein.
Idem est, 4. quoad curam Religionis, ut pote quae ad Dominos territoriales pertinet, & sequela est superioritatis territorialis indubitata, ita ut cuius regio, eius religio; is autem, qui merum Imperium, sive jurisdictionem criminalem tantùm habet, modum in religione praescribere vel eandem mutare nequit, infra lib. 3. cap. 1. n. 76.The same goes for 4., with respect to the care of Religion, since it pertains to the territorial Lords, and is undoubtedly a consequence of territorial sovereignty, thus whose the region, his the religion; he, however, who holds only merum imperium or criminal jurisdiction, cannot prescribe religious custom or alter the same, below, book 3, chapter 1, n. 76.1693, Philipp Knipschildt, Tractatus politico-historico-juridicus de juribus et privilegiis nobilitatis […] , page 235:

Literally, “Whose is the region, his is the religion”. Summary of the 1555 Peace of Augsburg.