Rick Santorum used a phrase from the presidential oath of office when asserting on CNN's "State of the Union" on Sunday that President Barack Obama crossed the line in an immigration directive he issued.
The oath is a pledge to "faithfully execute the office of President of the United States" and follow the Constitution.
"There's a difference between saying, 'I don't like the law. I wish, you know, I wish the law were different. But I'm the president. My job is to faithfully execute.' And he has not faithfully executed," Santorum told CNN Chief Political Correspondent Candy Crowley.
He said the selective enforcement of laws practiced daily by police officers is very different from the directive that deportations for some young people who are in the United States illegally be deferred, provided they arrived at a young age, have no criminal record, are not a security threat and are pursuing higher education.
"It's the difference between someone who is actually in the, you know, out there on the street, you know, making a call as to whether to charge someone with a crime," Santorum said, and having "a policy at the top saying we are going to carte blanche order people not to enforce the law."
Santorum and other Republicans sharply criticized the president following Friday's announcement, which some saw as political posturing.
The former senator from Pennsylvania has repeatedly criticized Obama for bypassing the congressional lawmaking process by issuing the directive.
"To me, the most outrageous thing was the process in which he did it," Santorum told Crowley.
When campaigning for the Republican presidential nomination, he often prefaced his answers to questions on immigration with the story of his father's move to the country at a young age. He said in the interview he doesn't "like a lot of the rhetoric and tone that I hear from some on our side," and that he understands "the sympathy for people who came here through no fault of their own."
Santorum also defended his endorsement of Dan Liljenquist to replace long-time Sen. Orrin Hatch of Utah, a fixture of the Senate with whom Santorum served from 1995-2007.
"It's not Orrin Hatch's seat. It wasn't my seat when I was in the United States Senate. In other words, nobody owns it," he said. "The people of Utah, just like the people of every other state, have an opportunity every time to assess who's the right person at the time."
One of Santorum's previous endorsements, for fellow Pennsylvanian Arlen Specter's 2004 re-election, came under criticism as Santorum's rivals argued he supported the man who cast the deciding Senate vote in favor of Obama's health reform law. Santorum said he backed Specter -- who was a Republican, then switched parties in 2009 -- in exchange for Specter's support of President George W. Bush's judicial nominees, a promise Specter said he never made.
Reflecting on his primary run this year, Santorum told Crowley that he stands by his statement in April -- shortly after ending his presidential bid -- that he regrets calling the president "a snob."
"That's the one I feel bad about," Santorum said on CNN's "Piers Morgan Tonight" at the time. He told Crowley that during the primaries, "sometimes the rhetoric might have, you know, gone over the line a bit."