Judge Andrew Napolitano, Fox News’ longtime senior judicial analyst, appeared on Fox & Friends early Thursday to teach the hosts a basic civics lesson in light of President Trump’s announcement this week that he plans to end birthright citizenship through an executive order.

Though hosts Brian Kilmeade and Steve Doocy appeared eager to find a method to carry out Trump’s proposed policy, Napolitano dashed their hopes with a sit-down worthy of a 7th-grade classroom.

“Look, the president can’t change the plain meaning of the Constitution with the stroke of a pen,” Napolitano said.

Trump’s intentions were revealed in a clip from the new Axios on HBO released this week. In it, he said he plans to sign an order that will terminate the legal right of babies born on U.S. soil to have citizenship if the parent is an undocumented immigrant or non-citizen.

“We’re the only country in the world where a person comes in and has a baby, and the baby is essentially a citizen of the United States... with all of those benefits,” Trump said, inaccurately. “And it has to end.”

(That claim was quickly deemed false after the Axios clip posted—birthright citizenship exists in dozens of other countries, including Canada and Mexico.)

Napolitano explained that the 14th Amendment of the U.S. Constitution “says that all persons born or naturalized in the United States and subject to the jurisdiction thereof are citizens of the United States and the state in which they live.”

“Congress can’t change the Constitution,” Napolitano made clear to the hosts. “If the president wants legislation that says, for example, that Congress declares that birthright citizenship no longer exists, that legislation would be just as unconstitutional as a presidential executive order declaring that birthright citizenship doesn’t exist.”

Doocy interjected: “But it’s that word ‘jurisdiction’—”

Napolitano continued: “Are illegals subject to the jurisdiction of the United States? Of course they are. They commit a crime, they get prosecuted. They get in an automobile accident, they can sue. They have basic human rights. They can’t vote, they can’t run for office, but they are subject to the jurisdiction thereof.”

Kilmeade chimed in: “But do you agree that our Founding Fathers couldn’t possibly have foreseen 20 million people here illegally and people abusing the system like Russians and Chinese, as well as Central and South Americans?”

Napolitano replied, “Of course, but the remedy is to change the Constitution, which is very difficult, very cumbersome and, in my opinion, will not happen. It would require a vote of two-thirds in both houses of Congress—that’s not going to happen now—and ratification by three-quarters of the state legislatures.”

Kilmeade, apparently hoping to still find a way around that lengthy process, asked, “How about legislation driven from [Sen.] Lindsey Graham that passes the House and Senate, that makes the court decide on this and have an honest debate about it?”

Napolitano replied: “The courts can’t just decide something. They have to have a real case or controversy in front of them.”

“When the Supreme Court has looked at this, candidly, it’s gone both ways. But the more recent cases have said, whoever is born here is an American citizen,” he added.

The judge also noted that if President Trump was capable of such an executive order, other presidents would have been, too, including Barack Obama.

“Presidents can’t do that ,” he said. “I think the president knows that. I believe he has generated this because he wants the debate, he thinks this debate will help Republicans in the five days remaining before the midterms. I don’t think he seriously thinks he can change the Constitution with an executive order.”