"I think you have one judge," Spicer told Fox News' Brian Kilmeade. "The law is very clear that the President has broad powers to keep this country safe and limit access to people that could come in to this country and do us harm."
He argued that Trump's order was a "very legal, constitutional" use of his power to ensure national security.
"And it's somewhat sad to see a judge go rogue like this," Spicer said. "It's a shame that we're not focused more on making sure that we are applauding the decision by the President to make a renewed focus on keeping this country safe."
U.S. District Judge James Robart on Friday blocked Trump's executive order, which temporarily bars visitors from seven predominantly Muslim countries from entering the United States and suspends the country's refugee program.
After Sally Yates was fired as acting U.S. attorney general last month for writing a letter to Justice Department lawyers ordering them not to defend Trump's travel ban, Spicer signaled that if federal employees should expect to be fired if they refuse to follow Trump's "orders."
"I think that that kind of comes with the job, right?" he told reporters. "Every one of the appointees understand that they serve at the pleasure of the President."