Ius indigenatus

Ius indigenatus (Latin for "right of local birth") is a right which was from the 15th to the 18th century a requirement for people to hold office in Prussia. It limited offices and land ownership to local Prussian natives, i.e. persons from the Monastic state of the Teutonic Knights as of 1453.

When the Prussian cities (some of them Hanseatic league members) and gentry (many of German origin) seceded from the Order in 1454, it was, along with Danzig's privileges, a prerequisite for a personal union with the King of Poland. It was confirmed in 1466 by the Second Peace of Thorn which secured a large decree of autonomy for Royal Prussia. The Prussian Ius indigenatus was valid for both parts of Prussia separated in 1466, the western part, later called Royal Prussia, and the eastern part, from 1525 the Duchy of Prussia, later East Prussia.

At times this Prussian birthright (nationality), has been frequently ignored by the Polish side in later centuries.

In Silesia, the Silesian Ius indigenatus was customary as well.

...
Wikipedia