Eric Holder's Justice Department green-lighted the decision not to notify Congress -- as required by law -- before the Pentagon traded five Taliban fighters for Army Sgt. Bowe Bergdahl last year, the Obama administration's point person on Guantanamo Bay policy testified Thursday. 

Speaking to the Senate Armed Services Committee, defense official Brian McKeon was questioned on what is still a sore spot for many members of Congress: that the administration went forward with the Taliban-Bergdahl swap without giving Congress the typically required 30-day notification. 

Sen. Thom Tillis, R-N.C., asked McKeon why Congress was not informed, "as per the statutes." 

McKeon said he understands the Department of Justice and the department's general counsel "interpreted the president's powers because of the security risks and safety of Sergeant Bergdahl necessitated proceeding without the 30-day notice." 

The rationale squares with what administration officials claimed last year -- that congressional notification could have risked jeopardizing the fast-moving negotiations to secure Bergdahl's freedom. 

But lawmakers have challenged that call ever since. 

Meanwhile, McKeon made clear at Thursday's hearing that the push to close Guantanamo Bay's prison camp is moving forward, despite lawmakers' lingering security concerns -- most recently, over a member of the "Taliban 5" apparently trying to make contact with the Taliban, while under supervision in Qatar. 

McKeon stressed that the administration considers it a national security priority to close the camp, in part because it is used by extremists to incite violence. 

He pointed to the recent execution of Jordanian and Japanese hostages by Islamic State terrorists. He said it is "no coincidence" that the videos showed the victims -- one of whom was burned alive, the other of whom was beheaded -- in orange jumpsuits, like those once worn by detainees at Guantanamo Bay. Such jumpsuits were also worn at the Abu Ghraib prison in Iraq. 

Republicans, though, argue that terrorists would find reasons to attack the West regardless, and certainly did so before Guantanamo was in operation. 

Fox News' Catherine Herridge contributed to this report.