Homeland Security adviser Tom Bossert speaks during the news briefing at the White House in Washington, Friday, Aug. 25, 2017. (AP Photo/Carolyn Kaster)

White House homeland security adviser Tom Bossert on Sunday defended President Trump's decision to pardon controversial former Arizona sheriff Joe Arpaio, a campaign supporter, calling it a “straightforward” case of clemency for an aging man with a history of military service.

Bossert denied accusations by lawmakers, including Sen. John McCain (R-Ariz.), who argued that the pardon demonstrates Trump's contempt for the rule of law.

“Just about every modern president ends up with some controversial pardons,” Bossert said on ABC News's “This Week with George Stephanopoulos.” “I don’t think it’s fair to characterize him as not caring about the rule of law.”

“I’m pretty certain that this is not something that will threaten our constitutional order,” Bossert added.

Bossert said he was not familiar with the details of the criminal contempt charges Arpaio faced over his failure to comply with a judge's order to end the practice of detaining people on suspicion that they had undocumented status. Critics called Arpaio's practices racial profiling.

Trump, in announcing the pardon, did not address the charges. Instead, at a rally in Phoenix this week, he defended Arpaio, who he said was being prosecuted for “doing his job.”

“It was a contempt order and not an issue of his job or not his job,” Bossert said. “I really don’t know the details of it.

“I think there’s a clemency argument that can be made for the long history of service, both in the United States military and in law enforcement, for the sheriff,” he added.