WASHINGTON • A divided Supreme Court on Tuesday upheld a broad conception of birthright citizenship, rejecting President Donald Trump’s executive order declaring that children born to people who are in the United States illegally or temporarily are not American citizens.

The justices relied on the dominant understanding of the 14th Amendment, adopted after the Civil War and more recent federal laws in ruling that anyone born in the country, with very limited exceptions, is a citizen.

“Citizenship, then and now, was the right to have rights — to freely participate in our political community. The Framers of the Fourteenth Amendment extended that promise to ‘every freeborn person in this land,’” Chief Justice John Roberts wrote for the court, citing congressional debate over the amendment, “We keep that promise today.”

Three conservative justices would have allowed the restrictions to take effect.

“The Court today takes the extraordinary step of holding facially unconstitutional the President’s Order excluding from citizenship the children of foreign temporary visitors and illegal aliens,” Justice Clarence Thomas wrote in a 91-page dissent. “In doing so, the Court adds to the sad history of the Fourteenth Amendment, which was designed and understood to secure equal rights for the freed blacks but has instead been repurposed for political projects that the Reconstruction Congress did not support.”

The Republican president’s restrictions had been blocked by several lower courts and had not taken effect anywhere in the U.S.

During arguments in April, both conservative and liberal justices questioned the order’s legality in a case that was magnified by Trump’s attendance in the courtroom.

The justices ruled on Trump’s appeal of a lower-court ruling from New Hampshire that struck down the citizenship restrictions.

The birthright citizenship order, which Trump signed on the first day of his second term, is part of his administration’s broad crackdown on illegal immigration.

Birthright citizenship was the first Trump immigration-related policy to reach the court for a final ruling. The justices previously struck down global tariffs Trump had imposed under an emergency powers law.

The Trump administration had argued that the common view of citizenship is wrong, asserting that children of noncitizens are not “subject to the jurisdiction” of the United States and therefore are not entitled to citizenship. The administration had maintained the 14th Amendment had never been interpreted, until more recently, to extend American citizenship broadly to everyone born within the U.S. The 14th Amendment states that “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.”

The Trump policy sought to exclude American citizenship to a child whose mother was illegally staying in the U.S. and the father was not a U.S. citizen or lawful permanent resident at the time of birth, or when the mother is legally but temporarily staying in the U.S., such as individuals with student and tourist visas.

In a series of decisions, lower courts have struck down Trump’s executive order as illegal. The decisions have invoked the high court’s 1898 ruling in Wong Kim Ark, which held that the U.S.-born child of Chinese nationals was a citizen.

More than one-quarter of a million babies born in the U.S. each year would have been affected by the executive order, according to research by the Migration Policy Institute and Pennsylvania State University’s Population Research Institute.