Answer:
Ex post facto
Step-by-step explanation:
Ex post facto is a latin expression that means “from what was done afterward”. It is simply the law that alters the regal consequences of any act that was done by an individual (which was legal at the time it was done) before the establishment of the law. In criminal law, It may change the penalty attached to any misdeeds; it could also make a crime look more serious when it gets enlisted in a more severe category other than were it was.
These laws are prohibited in Article 1, section 9, clause 3 of the constitution of the United States.