It’s one of the clearest sentences in the Constitution: 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.

It’s the first sentence of the 14th Amendment. In addition to establishing the basis for citizenship, the amendment ensures equal protection of the laws, sets the process to determine the number of representatives from each state, prevents someone guilty of insurrection from becoming an elected official and affirms the validity of the public debt.

In fact, that one sentence is a pretty small part of a pretty big amendment.

But it’s still part of the Constitution. And the President of the United States cannot nullify it.

President Trump has announced he wants to redefine citizenship so that the children of immigrants, even though they are born here, are not citizens. He says his legal experts have told him he can do so with a narrowly worded executive order.

We are not legal experts, but we clearly understand “all persons” to mean everybody.

The 14th Amendment was ratified three years after the Civil War. It’s intent was to define citizenship in a way that freed slaves would be considered citizens and therefore eligible for the equal protection of the law that the amendment guarantees.

Americans had been trying to define citizenship since 1790, relying on English common law that included the idea that a person born in a certain place owed loyalty to the leadership of that place — a person born in lands ruled by the King of England would be a subject of the English crown, and a person born in the United States would be a citizen of the United States. The Naturalization Act of 1790 added a way for immigrants — exclusively free white men, of course — to become citizens.

A mere five years later, Congress changed the path to citizenship, and that was merely the first of several changes over the years.

But Congress is free to make changes where the Constitution doesn’t take a stand, and with the 14th Amendment, approved by two-thirds of Congress as well as legislatures of three-fourths of the states, the Constitution takes a stand.

Which isn’t to say the matter was settled for good.

In 1898, the U.S. Supreme Court was faced with a case very relevant to today’s conflict over illegal immigration. Wong Kim Ark’s parents were Chinese immigrants living and working in San Francisco. He left the country on a trip and was denied re-entry when he returned. He argued he was a United States citizen by birth, and a divided Supreme Court agreed: “All persons born … in the United States …” did, indeed, mean everybody.

The difference between United States vs. Wong Kim Ark and today is that Wong’s parents were legal immigrants, and the current conflict revolves around those who are here illegally. The court has never ruled on that issue.

If Trump follows through with his executive order, you can bet it will get its day in court.