The US Justice Department on Saturday appealed a temporary block of Donald Trump's travel ban on citizens from seven mainly Muslim countries, after the president unleashed a fiery tirade and those with valid visas started arriving on American soil.
It was just the latest in a series of dramatic twists since the Republican billionaire leader issued his immigration order a week ago.
On Friday, a federal judge in Washington state put a temporary stay on the measures pending a wider legal review, prompting government agencies and global airlines to cease enforcing the ban.
Thousands of people from London and Paris to New York and Washington staged fresh protests against Trump, who took office on January 20 -- little more than two weeks ago.
The Manhattan property mogul-turned-president, who was spending the weekend at his Mar-a-Lago vacation retreat in Florida, unloaded a barrage of angry tweets throughout the day.
He specifically targeted US District Judge James Robart — an appointee of Republican president George W. Bush — in an extremely rare attack on a federal judge from a sitting president.
"The opinion of this so-called judge, which essentially takes law-enforcement away from our country, is ridiculous and will be overturned!" Trump tweeted early in the day.
In the evening, he posted: "The judge opens up our country to potential terrorists and others that do not have our best interests at heart. Bad people are very happy!"
Late Saturday, the Justice Department filed its motion to appeal, though the legal brief detailing its arguments has yet to come.
"We'll win. For the safety of the country, we'll win," Trump told reporters.
The case will now move to a federal appeals court.
Nevertheless, government authorities began complying with the lower court judge's ruling, reopening the borders to those with proper travel documents.
The State Department told visa holders from Iran, Iraq, Libya, Somalia, Sudan, Syria and Yemen that they are again allowed to travel as long as the documents had not been "physically cancelled."
The department earlier said up to 60,000 people had their visas revoked as a result of Trump's order, although a Justice Department attorney put the number at closer to 100,000.
The Department of Homeland Security — which runs border agencies — also said it would cease implementing the order.
The restrictions on all refugees and travelers from the seven countries went into effect a week ago, wreaking havoc at airports across America and leaving travelers trying to reach the United States in limbo.
The political backlash for Trump has been equally severe, with the order fueling numerous mass protests and White House infighting.
In Washington, hundreds of demonstrators marched from the White House to Capitol Hill, chanting "Donald, Donald, can't you see -- we don't want you in DC!"
About 3,000 people rallied in New York, while an estimated 10,000 people turned out in London, and smaller gatherings took place in Paris, Berlin, Stockholm and Barcelona.
Trump was forced to defend a botched rollout of the plan — which called his government's competence into question -- and fired the acting attorney general for refusing to defend the order in court.
His approval rating has sunk to the lowest level on record for any new president.
His latest rhetorical outburst is only likely to stoke the controversy.
Presidents from Thomas Jefferson to Barack Obama have criticized court rulings, but have rarely, if ever, criticized individual judges.
"I can't think of anything like it in the past century and a half at least," constitutional scholar and Harvard Law professor Laurence Tribe told AFP.
"It's not exactly contempt of court, but it certainly is contemptuous," said Tribe, who taught two sitting Supreme Court justices as well as Obama -- whom he later advised.
"It conveys a lack of respect for the independent judiciary that bodes ill for the country's future as long as Trump occupies the presidency," Tribe said.
Democrats in Congress were swift in their condemnation of Trump's remarks, while Republicans notably did not rush to his defense.
"This 'so-called' judge was nominated by a 'so-called' President & was confirmed by the 'so-called' Senate. Read the 'so-called' Constitution," tweeted California Democratic lawmaker Adam Schiff.
The White House has argued that the travel bans are needed in order to prevent terror attacks on the United States.
Experts from the fields of intelligence, counterterrorism and diplomacy say the ban is at best ineffective and at worst fuels hatred of the United States in the Middle East.
But cracking down on Islamist terror has become an organizing principle for Trump supporters and the White House has consistently sought to underscore the risks posed to Americans.
A recent Quinnipiac University poll showed 48 percent of voters favored "suspending immigration from 'terror prone' regions."
"When a country is no longer able to say who can, and who cannot , come in & out, especially for reasons of safety &.security - big trouble!" Trump tweeted Saturday.