The appeals court judges sparred with attorneys over the President's use of sweeping executive power, questioned the connection between the seven affected countries and terrorism, and launched into tough questions over whether the ban discriminated against Muslims.
During the telephone hearing, the lawyer representing the Justice Department, August Flentje, argued that the President had wide powers relating to immigration and national security. He contended that federal judges did not have the power to review Trump's executive order, which bars citizens of Iraq, Syria, Iran, Libya, Somalia, Sudan and Yemen from entering the US for 90 days.
It also prevents entry for all refugees for 120 days and indefinitely halts the admission of refugees from Syria.
From the start, Flentje repeatedly sought to emphasize the government's position that a lower court acted beyond his powers when it suspended the President's executive order last Friday. Flentje argued that the President acted within his constitutional powers.
"This is a traditional national security judgment that is assigned to the political branches and the President and the court's order immediately altered that," Flentje argued.
The three-judge panel at the Ninth Circuit Court of Appeals pressed Flentje on whether the government could show that the seven countries affected by Trump's ban were connected to terrorism.
"Has the government pointed to any evidence connecting these countries with terrorism," asked Judge Michelle Friedland.
Flentje, special counsel to the assistant attorney general at the Justice Department, countered that the lower court had overruled the President's judgment about the level of risk from those countries. "The district court's decision overrides the President's national security judgment about the level of risk and we've been talking about the level of risk that's acceptable," he said.
Judge Friedland fired back: "Are you arguing then that the President's decision in that regard is unreviewable (by a court)?"
Flentje paused and eventually answered, tentatively, "yes."
Judge Richard Clifton called the government's argument "abstract," noting that procedures were already in place to vet visa applicants.
Judge William Canby asked whether Flentje's logic could be taken to its most extreme conclusion: whether the President could simply say the United States will not admit Muslims into the country.
"Could he do that?" asked the judge. "Would anyone be able to challenge that?"
For the Justice Department, Flentje argued that the travel restrictions in Trump's executive order did not amount to a Muslim ban. "That's not the order," he said repeatedly.
But Judge Richard Clifton pressed him further. "We'd like to get to an answer to that question."
Eventually, Flentje capitulated and said a US citizen with a connection to someone seeking entry might be able to challenge the executive order if that were the case.
Intent to discriminate?
While the President's name was barely mentioned during the hearing, Trump's words were at the front of the judges' and attorneys' minds.
Washington state Solicitor General Noah Purcell, representing his state and Minnesota -- which are challenging the Trump executive order along with advocacy groups -- was pressed by Canby to explain how the executive order demonstrates a direct intent to discriminate against Muslims when only a relatively small percentage of Muslims hail from the seven banned countries.
"You don't have to prove it harms every Muslim -- you just need to show the action was motivated in part by animus," Purcell argued.
He alluded to comments made by Trump on the campaign trail, and by his ally, former New York City Mayor Rudy Giuliani, who claimed that Trump had asked him how a "Muslim ban" could be enacted legally. "There's rather shocking evidence of intent to discriminate," Purcell said.
Clifton shot back: "I don't think allegations cut it at this stage."
Flentje made the same point: "We're not saying the case shouldn't proceed. But it is extraordinary for a court to enjoin the President's national security determination based on some newspaper articles," he said.
At least two of the three judges appeared to accept the threshold issues of the case -- whether the plaintiffs have the ability, or legal standing, to sue.
Purcell, for Washington state, argued that the Trump administration could not demonstrate that it would suffer irreparable harm if the injunction is allowed to remain in place. On the other hand, state residents would suffer and state governments have lost tax revenue as a result of the executive order, he argued.
But Clifton also was skeptical of the state's argument on standing, wondering how many people in Washington would be harmed by the executive order.
"I suspect it is a small fraction," the judge said.
Flentje raised a fallback argument on behalf to the Justice Department, arguing that if the judges were inclined uphold the lower court's decision to block Trump's ban, then the ruling should at least be limited to people who have previously been admitted to the US. He argued that foreign nationals outside the US, who have never stepped foot on American soil, had no constitutional right to enter the country.
That argument didn't seem to get much traction: Purcell said it would not fully address the harms of the executive order.
"It would not remedy the order's violation of the establishment clause which harms everyone in our state ... by favoring one religious group over another. It also would not fully remedy the order's violation of the equal protection law -- denying some of our residents who are here, allowing them to receive those visits and so on," Purcell argued.
How will the court rule?
The Ninth Circuit has a reputation as one of the most liberal in the nation, to the point where some Republican lawmakers have even pushed to split it up in an effort to limit its impact.
But Kari Hong, an assistant professor at Boston College Law School, said Tuesday's hearing was technical in nature.
"The Ninth Circuit is often called a liberal court, but the issues they have to figure out today are dry and technical ones relating to standards of review and the deference owed to the lower court," Hong said. "Those issues will be resolved without regard to political preferences."
The President was kept up to date on the hearing by White House Counsel Don McGahn Tuesday night, CNN's Jeff Zeleny reported. A ruling is expected this week.
Correction: An earlier version of the story misstated Noah Purcell's title. He is the solicitor general of Washington state.