Okay kiddo, have you ever heard of history class before? It's when you learn about things that happened a long time ago and how they affected the world we live in now.
Well, the law of historical memory is sort of like a rule that some countries have to help people remember important events from their past.
Let's say that a really bad thing happened in a country a long time ago, like a war or people being treated unfairly. The law of historical memory says that the country should remember that event, so that they can learn from it and make sure it doesn't happen again.
Sometimes, the law of historical memory means that the country will create museums or monuments or have special ceremonies to honor the people who were affected by the bad thing that happened.
People who believe in the law of historical memory think that it's important to remember the past so that we can build a better future. Just like how you learn from your mistakes and try to do better next time, countries should do the same thing.