U.S. President Donald Trump signed an executive order hours after being sworn in that could lead to children born in the country no longer being deemed as citizens regardless of their parents’ status.

Trump promised during his campaign to become president he would end “birthright citizenship,” something opponents say creates an incentive for people to come into the U.S. illegally.

What is birthright citizenship?

Birthright citizenship allows for anyone born in the U.S. to be considered a citizen, regardless of whether their parents are also citizens of the country or they’re on a tourist visa or even living there illegally.

Legal experts say attempts to restrict that are likely to fail if challenged in court.

“It is very likely to fail because birthright citizenship is a constitutionally protected right guaranteed by the first sentence of the 14th Amendment, U.S. Constitution and upheld by previous Supreme Court decisions,” said Amanda Frost, a University of Virginia law professor.

The president’s executive order, however, questions that line and whether it extends citizenship to anyone born in the U.S. automatically.

Click to play video: 'Expert on Trump crackdown on illegal migrants'

Under Trump’s executive order, which would take effect 30 days from Tuesday, people are excluded from automatic citizenship if their mothers were not legally in the U.S. and fathers were not citizens or lawful permanent residents, or if their mothers were in the country legally but on a temporary basis and their father was not a citizen or legal permanent resident.

It also bars federal agencies from issuing documents recognizing citizenship, like a passport, or accepting documents issued by state or local governments.

Who does the order effect?

The Pew Research Center says in 2016, there were about 250,000 babies born to parents who did not hold legal status in the country, down from a peak of 390,000 in 2007.

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As of 2022, the most recent data available, the organization found there were 1.2 million U.S. citizens who were children of unauthorized immigrants living in the country.

In a lawsuit filed by 18 Democratic-led states and the District of Columbia on Tuesday, Massachusetts Attorney General Andrea Joy Campbell said in a statement that if Trump’s order were allowed to stand, more than 150,000 children born annually in the U.S. would be denied their right to citizenship for the first time.

Do other countries have birthright citizenship?

There are about 30 countries, including Canada and Mexico, that apply birthright citizenship — also known as jus soli or citizenship by birth on soil, according to World Atlas.

Others, like the U.K. and Australia, allow for automatic citizenship if one parent is a citizen or permanent resident, known as jus sanguinis.

In Canada, birthright citizenship does not apply to children of foreign diplomats or representatives of foreign governments. Canada also recognizes citizenship of children born to citizen parents abroad, but that cuts off after the first generation.

C-71, the federal bill that would have extended that ability to pass on citizenship by descent, died when Parliament was prorogued earlier in January.

But unlike in the U.S., Chantal Desloges, senior lawyer at Desloges Law Group, says reaction to the issue has not been always as prominent, except in the case of “birth tourism.” 

Click to play video: 'Trump says he ‘wanted a perfect document’ on birthright citizenship before signing'

“(It’s) where some people come to Canada as visitors, for example, with the sole purpose of simply having their child here in Canada to be born on Canadian soil and therefore be a Canadian citizen,” Desloges noted.

It’s one issue that Trump and other opponents have also cited as a reason to end it in the U.S.

While opposition to birthright citizenship has not been as vocal in Canada as in the U.S., Desloges said getting rid of it in Canada, as Trump is trying to do in the U.S., would have consequences, including potentially creating two classes of people.

“It is a very slippery slope when you start to create two classes of people in the same country,” she said. “If you change the fact of who is a citizen in Canada, then what’s to stop you from going further than that?”

Could the courts allow Trump’s order?

In addition to the 18 states suing, Trump’s order is also facing a challenge from several chapters of the American Civil Liberties Union.

While she said it likely wouldn’t proceed in court, Frost said if he appoints new Supreme Court justices who agree with restricting or limiting the guarantee, that could change.

“The way he would succeed would be if a court said your interpretation of the 14th Amendment is correct, we’ve been wrong all along, that everyone who assumed children born to undocumented immigrants were citizens were wrong all along and we have a new view or interpretation of the Constitution,” Frost said.

Outside of the courts, the only other option Trump would have to end such citizenship is by a constitutional amendment, but that would require approval by a two-thirds vote in both houses of Congress, and three-quarters of U.S. states.

with files from The Associated Press and Reuters