Nemo auditur propriam turpitudinem allegans is a civil law

Civil law (legal system)

Civil law is a legal system inspired by Roman law and whose primary feature is that laws are codified into collections, as compared to common law systems that gives great precedential weight to common law on the principle that it is unfair to treat similar facts differently on different...

 maxim

Legal maxim

A legal maxim is an established principle or proposition. The Latin term, apparently a variant on maxima, is not to be found in Roman law with any meaning exactly analogous to that of a legal maxim in the Medieval or modern sense of the word, but the treatises of many of the Roman jurists on...

 which may be translated into English

English language

English is a West Germanic language that arose in the Anglo-Saxon kingdoms of England and spread into what was to become south-east Scotland under the influence of the Anglian medieval kingdom of Northumbria...

 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.

On 30 June 1950, during the 475th meeting of the United Nations

United Nations

The United Nations is an international organization whose stated aims are facilitating cooperation in international law, international security, economic development, social progress, human rights, and achievement of world peace...

 Security Council when discussing the validity of resolutions made in the absence of one of the permanent members, the French delegate invoked the maxim.