"The rollout of this executive order was terrible," Christie told reporters in Newark, New Jersey. "The right people were not involved or consulted. There was confusion in the enforcement that went on here."
Christie was one of Trump's most prominent and ardent supporters after his own failed presidential campaign, but his role was diminished after the election when he was dismissed as transition chief and turned down a number of roles in the Trump administration.
"The President deserves much better than the rollout that he got of this plan," Christie said Tuesday. "A lot of the mistakes were made and those mistakes are unacceptable."
However, Christie demurred when asked about his concerns over Trump's senior staff.
"I know many of those folks. I'm not going to make any generalized statements about them," Christie said, while still placing the blame on their shoulders. "Anybody who looks at that objectively knows that wasn't the way it should have happened."
Christie also pushed back on the charge that Trump's executive order amounted to a "Muslim ban," which the New Jersey governor called "ridiculous" when Trump first announced it in 2015. Trump's order on Friday bars citizens from seven predominantly Muslim countries from entering the United States for 90 days, all refugees for 120 days and indefinitely suspends refugee admissions from Syria.
"He knew we disagreed about this topic when he was talking about a Muslim ban in general. We know that's not what this is, and he's backed off significantly from that from that position he had during the campaign," Christie said.
Christie explained how he and former New York City Mayor Rudy Giuliani pushed back on Trump's temporary ban when they came on board as supporters.
"I think in large part because a number of us told him we thought it was wrong, myself, Mayor Giuliani and others were vocal advocates when we joined his effort to convince him it needed to be something more narrow."
Green cards, issued to permanent residents, represent the "extreme vetting" that Trump talked about on the campaign, said Christie, but problems still remain in the overall vetting system.
"There is a big problem here and they're not taking the steps necessary to make sure that only those who have the right intentions enter our country. But it should be based, in my view, on intelligence, not on generalizations," said Christie.
Christie also leveled some criticism at "knee-jerk" reactions from Democrats who he said "have been a little bit shameful too."
"Mistakes were made and people need to stand up who made those mistakes of implementation. But also lets not be taking complete advantage of the situation for political gain as well," Christie said. I think that just makes the situation worse and doesn't make our country safer and that should be the goal."