Nulla poena sine lege

"Nulla poena sine lege" means that nobody can be punished if there is no specific law that says what they did is wrong.

Imagine you're playing a game with your friends and suddenly one of them says "you lose because you're wearing a blue shirt!" You would feel very confused and upset because there was no rule that said you couldn't wear a blue shirt.

In the same way, if there is no law that says you can't do something, then nobody can punish you for doing it. This is important because it helps us make sure that everyone is treated fairly and equally under the law.