United States v. Pelton is a court case from the United States Supreme Court. It is about whether a person can be convicted of a crime even if he or she didn't know that it was against the law.
The case involved a man named Pelton, who was accused of stealing government property. He did not know that it was against the law, but the government argued that he should still be convicted.
The Supreme Court decided that even if a person doesn't know the law, they can be convicted if they should have known that what they were doing was wrong. Basically, this means that everyone is expected to know the law even if they haven't been told.