State Assemblyman Tim Donnelly from Twin Peaks was detained last month after a Colt .45 and several rounds of ammunition were found in his carry-on bag at the airport on Jan. 4.
The Republican, who's an outspoken gun rights advocate, said he brought the weapon to his garage while he was home alone because he had received death threats over his opposition to illegal immigration. He said he hid it in his briefcase so his wife would not be alarmed when she came home, then forgot it was there.
"Several weeks ago, I made an innocent mistake for which I have taken responsibility," Donnelly, 45, said in a statement. "I have fully cooperated with law enforcement officials and have been candid about this matter publicly."
He could face a $1,000 fine and up to a year in county jail on the first charge, and a $1,000 fine and up to six months in jail on the second charge if he is convicted.
The Associated Press contributed to this story.