A federal judge in Seattle on Friday put a nationwide block on US President Donald Trump's week-old executive order barring nationals from seven countries from entering the United States.
The judge's temporary restraining order represents a major challenge to Trump's action, although his administration could still appeal the ruling and have the policy upheld.
The Seattle judge, James Robart, made his ruling effective immediately on Friday, suggesting that travel restrictions could be lifted straight away.
"It's a wonderful day for the rule of law in this country," said Washington state solicitor general Noah Purcell.
The state's attorney general, Bob Ferguson, said: "This decision shuts down the executive order right now." He said he expected the federal government to honor the ruling.