Immigrant and civil rights advocates, including the American Civil Liberties Union, filed a lawsuit against a birthright citizenship executive order signed by Republican U.S. President Donald Trump after taking office on Monday.

Legal experts said the president’s executive order would upend precedent and is unlikely to pass constitutional muster

A president cannot amend the Constitution by himself, and a Trump order to end birthright citizenship would doubtless face lawsuits. During his first term, he promised to end birthright citizenship but took little action to do so.