If you were born in the United States, you are an American citizen. That has been the law of the land since 1868. On Wednesday, the Supreme Court will decide whether that still holds true.

The justices will hear oral arguments in Trump v. Barbara, a case centered on President Trump's executive order signed on Day 1 of his second term that seeks to deny automatic citizenship to children born in the U.S. if their parents are undocumented or in the country on a temporary visa. Every lower court that has reviewed the order has blocked it, calling it unconstitutional. Now it is the Supreme Court's turn.

A ruling is expected by late June or July. What the justices decide will either cement more than a century of settled constitutional interpretation or hand Trump the most consequential immigration victory of his presidency.

The legal foundation for birthright citizenship is the 14th Amendment, ratified after the Civil War specifically to undo the Supreme Court's Dred Scott decision, which had ruled that Black people, enslaved or free, could never be American citizens. The amendment states that anyone "born or naturalized in the United States and subject to the jurisdiction thereof" is a citizen. Congress reinforced that language in federal statute in 1940 and again in 1952.

For over 125 years, that clause has been broadly read to mean that virtually any baby born on American soil is automatically a citizen, with two narrow exceptions: children of foreign diplomats and children of enemy combatants born during an occupation. Trump's order pushes for a third exception: the children of undocumented immigrants and those on temporary visas.

The White House argues the 14th Amendment was never meant to go that far. In court filings, Solicitor General D. John Sauer contends the amendment was written to protect freed Black Americans and their descendants, not to extend citizenship to every child born within U.S. borders regardless of their parents' legal status. The phrase "subject to the jurisdiction thereof," the administration argues, was always meant to exclude people with no permanent legal ties to the country.

Sauer has also pointed to the 1898 Supreme Court case United States v. Wong Kim Ark, which the administration reads as limiting birthright citizenship to children of parents with a permanent legal residence in the U.S. Legal scholars and opponents of the order widely dispute that interpretation of the ruling.

Ahead of Wednesday's arguments, Trump took to Truth Social to frame the issue in stark terms, claiming birthright citizenship was only ever about "the babies of slaves" and has been wrongly extended to children of immigrants. The post drew immediate pushback from historians and constitutional law experts.

The stakes are not abstract. According to research from the Migration Policy Institute and Penn State's Population Research Institute, more than 250,000 babies born in the U.S. each year would be denied citizenship under Trump's order. Those children would effectively be stateless, without the legal protections, documentation, or rights that come with U.S. citizenship.

Three plaintiffs whose children were born in the U.S. and face that outcome filed a class-action lawsuit last July with support from the ACLU. A federal judge ruled in their favor, and the Supreme Court in December agreed to skip the appellate process and take the case directly.

"We have the president of the United States trying to radically reinterpret the definition of American citizenship," ACLU Legal Director Cecillia Wang, who will argue before the justices Wednesday, told CBS News.

The case lands at the Supreme Court after the justices delivered Trump a significant defeat in February, striking down sweeping tariffs he had imposed using emergency powers. Trump responded by publicly attacking the two conservative justices he appointed who voted against him and writing on Truth Social that the court "will find a way to come to the wrong conclusion" on birthright citizenship.

Norm Eisen, co-founder of Democracy Defenders Fund and co-counsel with the ACLU in this case, told CBS News the court "has started to push back" on Trump's second-term agenda. "The high court is joining the trial and appellate courts in barring Donald Trump's illegal action," Eisen said, "and they should do the same when it comes to birthright citizenship."

Even some voices on the right are skeptical of the administration's position. A coalition of 28 Republicans, including former Trump White House lawyer Ty Cobb and former federal judges, filed a brief calling the executive order "a brazen attempt by the President to assert power that the Constitution denies him."