Question

punishing someone for an action that did not used to be a crime is an example of
an ex post facto law.
habeas corpus.
a “necessary and proper” law.
a bill of attainder.

Explanation:

• An ex post facto law punishes people for acts that were not crimes when committed.
• Habeas corpus is a legal action to challenge unlawful detention.
• A "necessary and proper" law refers to congressional implied powers.
• A bill of attainder punishes a specific individual/group without trial.

Answer:

an ex post facto law.