Nullum crimen, nulla poena sine praevia lege poenali

Okay kiddo, so there's this rule called "nullum crimen, nulla poena sine praevia lege poenali" which is Latin for "no crime, no punishment without a previous penal law." Basically, it means that before someone can be punished for doing something wrong, there has to be a law that says that thing is wrong. It's kind of like playing a game - you have to know the rules before you can get in trouble for breaking them. This rule helps to make sure that everyone is treated fairly and that people can't just make up punishments on the spot without a good reason. So, always remember to follow the rules and know when you might be doing something that's not allowed!