A US senator bemoaned Thursday morning that the constitutional right to due process “is what’s killing us right now.”

Democratic Sen. Joe Manchin said on MSNBC’s “Morning Joe” that the right to due process, guaranteed by the Fifth Amendment of the US Constitution, had made it difficult to pass gun-control legislation denying those on the FBI’s terror watch list the ability to purchase a firearm.

“The firewall we have right now is due process,” the West Virginia senator said. “It’s all due process.”

.@Sen_JoeManchin: Due process is what's killing us right now https://t.co/OTf9LnxHXZ — Morning Joe (@Morning_Joe) June 16, 2016

In the aftermath of the Orlando terror attack, which claimed the lives of 49 people, Democrats have renewed calls for legislation aimed at blocking individuals on the terror watch list from being able to buy a gun. Republicans have argued against such legislation, contending it would be wrong to strip citizens of their Second Amendment right without being convicted of a crime.

Manchin noted that the FBI “did everything they were supposed to do,” but had “no way” of blocking the Orlando attacker from purchasing a firearm. The bureau conducted two investigations into the shooter, 29-year-old Omar Mateen, but closed both after determining he was not a threat.

“There was no way to do that,” he said.

The senator floated the idea of enacting a five-year cooling period, something he said could perhaps garner bipartisan support.

“So can’t we say that if a person is under suspicion, there should be a five-year period of time that we have to see if good behavior, if this person continues the same traits?” he asked. “Maybe we can come to that kind of an agreement.”

He added: “But due process is what’s killing us right now.”