This phrase is not exactly slang, but a popular saying in Spanish. It literally translates to 'A thief who steals from another thief deserves forgiveness'. It is used to express the idea that if a person does wrong to someone who also does wrong, the action can be justified or is less severe.
Examples
- Spanish: Juan robó al estafador que nos había engañado a todos, así que, como dice el dicho, 'ladrón que roba a ladrón, merece el perdón'.
- English: Juan stole from the con artist who had deceived us all, so, as the saying goes, 'a thief who steals from another thief deserves forgiveness'.