The so-called Navy-Blue Police (Policja granatowa, nicknamed after the color of their uniforms) were used as an auxiliary unit of the Gestapo and Kripo, yet they had no means of executing law and order in the occupied country.
At the same time, the German police forces and courts were more interested in persecution of Jews and members of the Polish intelligentsia and underground rather than common criminals.
First underground, ad hoc courts were created alongside some of the first Polish resistance organizations as early as in 1939.
No citizens of other states (including members of the occupying forces of Germany and the USSR) were ever sentenced by the Underground Courts.
The reason for such a policy was a belief that the Polish Underground State should act as if the occupation and dismemberment of Poland never happened.