The 14th Amendment

The citizenship clause says: "All persons born or naturalized in the United States and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside." The second sentence contains two of the most important clauses in the Constitution, the due process and equal protection clauses. They apply to everyone in the U.S., not just citizens: "No State shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any State deprive any person of life, liberty or property, without due process of law, nor deny to any person within its jurisdiction the equal protection of the laws."