A federal judge Thursday blocked President Donald Trump’s executive order outlawing birthright citizenship —the policy automatically giving citizenship to anyone born in the U.S.—and declared it “blatantly unconstitutional,” as legal experts widely believe the president does not have the power to change the policy on his own.

U.S. District Judge John Coughenour, appointed by former President Ronald Reagan, signed the temporary restraining order on Thursday to block Trump’s action. Coughenour’s decision just days after a number of states, including New Jersey, sued the Trump administration over the move.