Government Glossary
Ex Post Facto Law
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.
Plain-English Meaning
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.