Postal censorship

Well kiddo, you know how when we send a letter or package through the mail, it has to go through certain people and machines to make sure everything is safe, right?

Well, sometimes those people and machines can also check to see what's inside the letter or package. And if they think there's something in there that's not allowed or might be dangerous, they can choose not to deliver it to the person it was meant to go to. This is called postal censorship.

It's kind of like if you were playing a game of tag, and the person who is "it" is also checking to make sure you're not hiding anything in your pockets or backpack that could be dangerous or unfair to the other players. If they find something, they might say you can't play anymore.

Of course, the people who are checking the mail have rules and guidelines they have to follow to make sure they're not just stopping things for no reason. But sometimes, people don't like the idea of someone else reading or checking their mail without their permission.