A day after President Donald Trump issued an executive order barring birthright citizenship to children of undocumented residents, the American Civil Liberties Union of New Hampshire sued in the U.S.

Until the order, which Trump signed the same day he was inaugurated as the 47th president, the U.S. government has, at least the late 1800s, considered the child of any immigrant born on U.S. soil an automatic citizen, even to a mother in the United States illegally.

The president’s executive order to end birthright citizenship will affect more than 11 million immigrants as well as more than 580,000 people with H1-B visas.