According to the U.S. Constitution, Congress cannot grant individuals or groups titles of nobility, pass laws that punish specific individuals or groups, retroactively make something illegal or suspend people's right to know why they are being charged with a crime. This is except in cases of emergency.
Article I, Section 9 of the U.S. Constitution describes powers that Congress does not have. When the United States adopted the Constitution, many politicians wanted to place stronger restrictions on Congress. The Bill of Rights further limited federal power, including prohibiting Congress from restricting free speech. The 27th Amendment to the Constitution prevents members of Congress from raising their own pay until the next Congress comes into session.