Members of the Trump administration have spoken recently about possibly suspending a foundational principle of the Constitution, habeas corpus, which protects people from unlawful detention.

Kristi Noem, the homeland security secretary, incorrectly described it in a Senate hearing on Tuesday as the president’s “constitutional right” to deport people.

Ms. Noem also said that she thought the president had the authority to suspend habeas corpus, an action that has been weighed by Trump officials, though legal experts say that can only be done by Congress. Here’s how habeas corpus works:

What does habeas corpus do?

Habeas corpus, which is enshrined in the first article of the Constitution, helps ensure that people are not detained without valid legal grounds.

If someone believes a person is being illegally detained, they can ask a judge to issue a “writ” of habeas corpus — basically a court order — demanding that the party detaining the person bring them into court and prove that they have the authority to do so. If the judge finds that they do not, the detainee must be set free.

Amanda Tyler, a constitutional law professor at the University of California, Berkeley, called habeas corpus “one of the single most foundational aspects of American law and the American constitution.”

“What it does is empower courts to protect individual liberty,” Professor Tyler said. “It’s hard to imagine what could be more central to the role of courts in our constitutional structure.”