This type of law criminalizes an act retroactively, and is not allowed under the Bill of Rights.

• A. Ex Post Facto
• B. Habeas Corpus
• C. Bill of Attainder
• D. Due Process

Answer: (A)

The main idea here is retroactive criminalization—making an act illegal after it’s already been done or increasing penalties for something that was legal when it occurred. Ex post facto laws do exactly that, and the Constitution forbids them because they punish people based on laws that didn’t exist at the time of their actions, undermining fairness and predictability in law.

Habeas corpus is a protection against unlawful detention, not retroactive punishment. A bill of attainder is a law that punishes a person or group without a trial, rather than retroactively criminalizing an act. Due process refers to fair and proper legal procedures, not retroactivity itself. So the term that best fits the description of retroactive criminalization is ex post facto.