President Donald Trump says he wants to use an executive order to end birthright citizenship for children born in the US to unauthorized immigrant parents.

Trump made this declaration after a question from reporter Jonathan Swan in a taped interview with Axios for the website’s coming HBO special. It’s not an announcement of a policy the White House is about to sign — it’s not at all clear what the timetable would be on the executive order, or even if there is one yet.

While most people assume that the text of the 14th Amendment — which says that all persons born in the US and “subject to the jurisdiction of its laws” are citizens — clearly applies to everyone regardless of parents’ immigration status, the Supreme Court has never explicitly ruled that this applies to the children of unauthorized immigrants. That’s the gap that Trump is hoping to exploit with a new executive order.

Trump justified his desire for the new executive order with a lie about how common it is for a country to extend automatic citizenship to everyone born on its soil. (He claims the US is the only country that does this; in fact, more than 30 do.)

For decades, including during a wave of immigration that has resulted in the most settled population of unauthorized immigrants in American history, the US has unconditionally treated children born in the US to unauthorized children as US citizens. Changing that would be a radical move. Doing it with the stroke of the pen would be a major power grab — and a dare for the federal courts to stop him. And it would be in the service of a goal that makes even a lot of conservatives very, very nervous.

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There is no reason to believe that an executive order to end birthright citizenship is imminent

Trump didn’t give Axios a timetable for when he planned to sign the executive order; he just said it was something he was going to do. (He claimed, “It’s in the process, it’ll happen,” but gave no other details.) Trump lies all the time, including about things he has done or will do. The administration has hyped up its anti-immigrant rhetoric in the last days before the midterm elections, including sending more than 5,000 troops to the US-Mexico border as a migrant caravan makes its way north.

While Axios appears to have been aware for a while of Trump’s plans to challenge the interpretation of the 14th Amendment, it’s not clear that those plans have gone beyond the White House (including the White House counsel’s office).

A lot more would have to be done before an executive order were ready for Trump to sign; it would need extensive review from the Department of Justice (specifically the Office of Legal Counsel) to assess its legality, and from the Department of Homeland Security and other departments to work out consequences.

The Trump administration has an aggressive immigration agenda already. Trump himself doesn’t singlehandedly determine what they focus on or when. And it’s simply not clear that this is a priority. In other words, the president’s remarks to Axios are better described as Trump talking about a thing he wants to do than Trump talking about a thing he’s definitely going to do, much less already doing.

Trump would be forcing a constitutional question by daring the courts to stop him

Current Supreme Court precedent (under the 1898 ruling known as Wong Kim Ark) holds that the children of noncitizens born in the United States are citizens.

Trump and the critics of universal birthright citizenship are correct that the Supreme Court has never explicitly held, as a matter of law, that children of unauthorized immigrants born in the United States are citizens. (It has assumed that they are; in the 1985 case INS v. Rios-Pineda, in which the parent of two US-born children challenged his deportation order, the Court referred to the children as US citizens by birth. But because the Court didn’t make a formal legal finding in this regard, the statement was just dicta, or rhetoric.)

That doesn’t mean the executive branch has the power to unilaterally clarify what the Supreme Court meant. In practice, Trump signing an executive order redefining birthright citizenship would be a way to bring the issue to the attention of the Supreme Court — doing what he wants, and daring a conservative court with two Trump-appointed justices to stop him.