Government Glossary

Ex Post Facto Law

Short Definition

An Ex Post Facto Law retroactively makes conduct criminal or increases criminal punishment after the conduct occurred. The Constitution forbids ex post facto criminal laws because people must be able to know the law before they can be punished for violating it.

Long Explanation

In practice, Ex Post Facto Law is useful because it helps a visitor connect a word or phrase to law making, committee work, oversight, votes, or congressional records. When you see the term in an official source, ask which office has authority, what decision is being made, which deadline or rule matters, and where the public record can be checked.

Examples

Simple exampleA visitor sees “Ex Post Facto Law” while reading about a bill and uses Congress.gov or a committee page to find the official record.

Civic exampleA citizen trying to follow lawmaking checks the bill text, committee action, vote record, and chamber rules before relying on a summary.

Common Misconception

A common mistake is treating Ex Post Facto Law as a complete explanation of what Congress did. The term is usually a starting point. To know what happened, check the bill text, committee action, chamber record, and vote information where available.

Related Terms

ConstitutionRightsCongressJudicial

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