U.S. District Senior Judge James Robart of Seattle on Friday issued a nationwide restraining order blocking the travel ban put in place by President Trump last week.
Trump's ban, created through an executive order, sought to block people from seven majority-Muslim countries from entering the United States.
In issuing his decision, Robart was siding with Washington Attorney General Bob Ferguson, who filed a suit to block key provisions of the president's executive order, which also bars Syrian refugees from entering the country.
White House press secretary Sean Spicer released a statement Friday night saying the Department of Justice would seek an emergency stay of this "outrageous order."
"The president's order is intended to protect the homeland and he has the constitutional authority and responsibility to protect the American people," Spicer said in the statement.
Washington state Gov. Jay Inslee, a Democrat, hailed Ferguson and applauded the decision.
"We should feel heartened by today's victory and more resolute than ever that we are fighting on the right side of history," the governor said in a statement. "Thank you to (Attorney General Bob Ferguson) and his team for making the case that no person - not even the president - is above the law."
Amnesty International also applauded the development.
"This decision is a short-term relief for thousands of people whose lives have been upended, but Congress must step in and block this unlawful ban for good," organization spokesman Eric Ferrero said in a statement. "Trump's Muslim ban is in humane, unlawful, and discriminatory, which is why the courts and the public want it to be stopped."
Ferguson said his team has been working around-the-clock for the last week on reversing the executive order.
"It's obviously an historic decision and an important one for the rule of law and for the people of the state of Washington and the people of our country. I have said from the beginning: it is not the loudest voice that prevails in the courtroom, it is the Constitution, and that's what we heard from Judge Robart today."
The decision is effective immediately nationwide, Ferguson said.
A lawyer with the national office of the American Civil Liberties Union said the decision was significant.
"The decision in Washington reaffirms that the courts will stand up to the president," said Lee Gelernt, the lawyer who successfully argued for a restraining order against Trump's ban in federal court in Brooklyn, N.Y.
"The courts have and will continue to recognize that this executive order favors Christians and disfavors Muslims and that is antithetical to American values and flatly inconsistent with the United States Constitution."
Word of the decision came shortly after revelations about an earlier decision by U.S. District Judge Nathaniel Gorton out of Boston, who refused to extend a temporary order that allowed some people affected by Trump's ban to enter the country.
Gorton ruled that the American Civil Liberties Union failed to demonstrate a need for an ongoing restraining order, according to the Globe.
The ACLU and other advocacy groups were aiming to extend the restraining order. Trump's stay affected travelers coming in from seven majority-Muslim countries and spurred protests at airports across the country.
With today's decision in place, it is now up to federal goverment to try to seek an appeal, Washington Solicitor General Noah Purcell said. The Washington state officials will confer with the federal government over the next several weeks, he said.