Nemo auditur propriam turpitudinem allegans

Nemo auditur propriam turpitudinem allegans is a civil law maxim which may be translated into English as "no one can be heard to invoke his own turpitude" or "no one shall be heard, who invokes his own guilt". The maxim operated with another, in pari causa turpitudinis cessat repetitio (where both parties are guilty, no one may recover), to preclude a court from intervening in a dispute involving an unlawful transaction.

Source: Wikipedia — Nemo auditur propriam turpitudinem allegans (CC BY-SA 4.0)