Ignorantia juris non excusat

Ignorantia juris non excusat[1] or ignorantia legis neminem excusat[2] (Latin for "ignorance of the law excuses not"[1] and "ignorance of law excuses no one"[2] respectively) is a legal principle holding that a person who is unaware of a law may not escape liability for violating that law merely by being unaware of its content.

European-law countries with a tradition of Roman law may also use an expression from Aristotle translated into Latin: nemo censetur ignorare legem (nobody is thought to be ignorant of the law) or ignorantia iuris nocet (not knowing the law is harmful).[citation needed]