A more thorough explanation:

An act of attainder is a special legislative act that imposes punishment, such as a death sentence or imprisonment, on a person or group without a trial. It is also known as a bill of attainder.

For example, in the past, a bill of attainder was used to sentence someone to death without a trial. This was considered unconstitutional and is now prohibited by the U.S. Constitution.

Another example of a bill of attainder is when a specific person or group is punished without a trial. This is also unconstitutional and violates the principle of due process.

These examples illustrate how an act of attainder is a violation of the constitutional rights of individuals and groups. It is important to uphold the principle of due process and ensure that everyone has a fair trial before being punished.