This week, the U.S. Supreme Court will hear arguments on what has long been an unquestioned, fundamental right: whether children born in the U.S. are automatically Americans by birth, a right guaranteed under the 14th Amendment and a concept that the high court itself has, for over a century, failed to turn its back on.

Justices are hearing the case Trump v. Barbara, a class-action challenge to President Donald Trump’s highly-contentious executive order, which declared an end to birthright citizenship for anyone born to undocumented or temporary resident parents after Feb. 20, 2025.

The stakes are enormously high for thousands of children and mixed-status families, whose legal rights and national status hang in the balance. Cody Wofsy, one of the American Civil Liberties Union lawyers arguing before the Supreme Court in defense of the existing system, told HuffPost it would completely upend the existing understanding of citizenship. “The arguments that the government is lodging about what it thinks the Constitution supposedly means would cast out the citizenship of millions and millions of people who have lived their entire lives as Americans, potentially going back generations,” he said.