Capitol Police apprehended Ty Carroll Mitchum, 59, of Clearwater, Fla., at the White House's West Front Sunday afternoon, Roll Call reported.
Mitchum told police he had the weapons in his car and allowed officers to search his car.
Police found three firearms and several rounds of ammunition in Mitchum's vehicle, a police statement said.
Mitchum was arrested without incident and charged with possession of an unregistered firearm and possession of unregistered ammunition.
Biologists detail four new deep-sea 'killer sponges'
Pistorius testifies he didn't consciously pull trigger when he shot girlfriend