Ever feel like the rules changed after you already played the game? That's the essence of *ex post facto* laws. The term, Latin for 'from after the action,' refers to laws that retroactively criminalize actions that were legal when committed, increase the punishment for a crime after it was committed, or alter the rules of evidence in a way that makes conviction easier after the fact.
Imagine this: you legally bought a certain type of fireworks last year. Now, a new law bans those fireworks and suddenly you're a criminal for owning them, even though your purchase was perfectly legal. That's an *ex post facto* law in action.
Why are these laws frowned upon? They violate fundamental principles of fairness and due process. People should be able to know what the rules are *before* they act, and governments shouldn't be able to unfairly target individuals by retroactively changing the law to fit their circumstances. The U.S. Constitution explicitly prohibits *ex post facto* laws, protecting us from this kind of legal time warp.
