A US judge in Seattle has issued a temporary nationwide block on President Donald Trump's ban on travellers from seven mainly Muslim nations.
Federal District Judge James Robart ruled against government lawyers' claims that US states did not have the standing to challenge Mr Trump's executive order.
The judge's order represents a major challenge to the Trump administration, which is expected to immediately appeal. The judge declined to stay the order, suggesting that travel restrictions could be lifted immediately.
Shortly after the ruling, US Customs and Border Protection told airlines to board travelers affected by the ban.
Last week's move by Mr Trump triggered mass protests and has resulted in confusion at US airports.
The State Department said 60,000 visas had since been revoked.
Mr Trump's executive order brought in a suspension of refugee admissions for 120 days.
There is also an indefinite ban on Syrian refugees. Anyone arriving from Iraq, Syria, Iran, Libya, Somalia, Sudan, and Yemen faces a 90-day visa suspension.
The challenge was brought by the state of Washington and later joined by the state of Minnesota.
"It's a wonderful day for the rule of law in this country," Washington state solicitor-general Noah Purcell said.
The decision came on a day that attorneys from four states were in courts challenging Mr Trump's executive order.
The Trump administration justified the action on national security grounds, but opponents labeled it an unconstitutional order targeting people based on religious beliefs.
Overnight (NZT), another federal judge ordered the White House to provide a list of all people stopped from entering the United States by the travel ban.
The Department of Homeland Security has issued a clarification of the order, stating there were no plans to extend it beyond the seven countries. The department also reiterated that the ban did not apply to permanent residents, or green card holders, and some others, such as those who have helped the US military.