mixtum imperium

Etymology
Literally “mixed” or “composite power”, “composite authority”. According to, mixtum denotes a mixture of and.

Noun

 * 1)  The delegable authority of a judge to execute penalties, primarily in civil cases.
 * 2)  The authority of lower magistrates, especially over private matters; a subsidiary form of authority dependent on the higher.

Usage notes
In the Middle Ages, often found in the collocation merum et mixtum imperium to denote unconstrained independence or legislative sovereignty.