When Mr. Landor reported for a five-month sentence for drug possession in Louisiana, he had not cut his hair for almost two decades, in keeping with his faith. His dreadlocks fell nearly to his knees.

Four months into his term, in 2020, he was transferred to a new prison. He carried with him a copy of a 2017 legal opinion that held that inmates must be allowed to keep their dreadlocks under a federal law protecting prisoners’ religious freedom.

When he pulled out a copy of that decision, a guard threw it in the trash, according to court documents he filed in a later lawsuit.

Two guards then handcuffed Mr. Landor to a chair and forcibly shaved him bald.

Six of nine on the Supreme Court belong on the other side of the courtroom.