The Trump administration is pushing for the the U.S. Supreme Court to allow some restrictions on birthright citizenship even as legal battles continue over President Donald Trump’s orders to end what has long been seen as a constitutional promise.

On Thursday, the administration filed emergency applications with the high court that would allow citizenship to be denied to people born in the U.S. after Feb. 19 if their parents are in the country illegally.

District judges in Maryland, Massachusetts and Washington have blocked the order, which Trump signed shortly after taking office in January. It is currently blocked nationwide.

Birthright citizenship automatically makes anyone born in the United States an American citizen, including children born to mothers in the country illegally. The right was enshrined soon after the Civil War in the Constitution’s 14th Amendment.

Trump and his supporters have argued that there should be tougher standards for becoming an American citizen, which he called “a priceless and profound gift” in his executive order.

Legal scholars, though, have said its the 14th Amendment’s constitutional protections would make it it extremely difficult to overturn.

Here is a look at birthright citizenship, what Trump has said about it and the prospects for ending it:

What Trump has said about birthright citizenship

Trump has said for years that he wants to end birthright citizenship.

“It’s ridiculous. We are the only country in the world that does this with the birthright, as you know, and it’s just absolutely ridiculous,” he said in January. Dozens of countries, mostly in the Americas, have birthright citizenship.

Opponents say the practice encourages people to come to the U.S. illegally so their children can have citizenship. Others argue that ending birthright citizenship would profoundly damage the country.

Its elimination “could eventually place every single person in America in the precarious position of having to prove American citizenship,” Alex Nowrasteh, vice president for economic and social policy studies at the pro-immigration Cato Institute, wrote after Trump’s order.

In 2019, the Migration Policy Institute estimated that 5.5 million children under age 18 lived with at least one parent in the country illegally in 2019, representing 7% of the U.S. child population. The vast majority of those children were U.S. citizens.

What does the law say?

Congress ratified the 14th Amendment in July 1868, soon after the Civil War.

“All persons born or naturalized in the United States and subject to the jurisdiction thereof, are citizens of the United States,” the amendment says.

But it didn’t always apply to everyone. It wasn’t until 1924, for example, that Congress granted citizenship to all Native Americans born in the U.S.

Supporters of immigration restrictions, including Trump, have argued the words “subject to the jurisdiction thereof” allow the U.S. to deny citizenship to babies born to women in the country illegally.

What is the basis of this legal appeal?

The emergency appeal does not focus directly on whether the presidential order is legally valid. Instead, it is aimed at the broad reach of orders issued by federal judges.

The Justice Department argues individual judges lack the power to make their rulings go into affect nationwide. Five of the Supreme Court’s conservative justices have raised concerns in the past about these nationwide injunctions. The high court, though, has never ruled on the matter.