Final answer:
A "bill of attainder" is a law that punishes an individual without a trial or fair hearing, and it, along with any "ex post facto laws", is expressly prohibited in the U.S. Constitution to maintain the fundamental right to due process.
Step-by-step explanation:
The law that punishes a person accused of a crime without a trial or a fair hearing in court is called a bill of attainder. Under such a law, individuals can be declared guilty and punished without the due process of a judicial proceeding. This practice was commonly used in England but was explicitly prohibited in the United States to safeguard citizens' rights to fair trials.
Additionally, the Constitution also outlaws ex post facto laws, which criminalize actions retroactively or increase the punishment for actions after they have been committed. Both types of laws would infringe upon the essential rights outlined in the U.S. Constitution, specifically the right to a fair trial and protection against retroactive punishment.
The prohibition of these laws ensures that all individuals are granted the right to due process, which includes a hearing before a judge, the right to be informed of accusations, and the right to legal representation. Violating these principles would undermine the legal foundation upon which the judicial system is built.