Mendocino County sheriff's deputies checked on a truck parked in a rural area and found a sleeping driver, a large beer bottle nearby and several guns inside the cab and in the bed of the truck, officials said.
The truck was parked in the 4-mile Glade area of Cow Mountain, near the Mendocino-Lake county line, officials said.
Deputies patrolling the area stopped at about 2:30 p.m. Sunday to check on the truck, which they thought was unoccupied.
They found a man asleep across the seat. A 40-ounce beer bottle was perched on the steering wheel, officials said.
Deputies awakened driver Dmetri Amaya, 50, who gave them permission to search the truck. They found two of the guns had been stolen, one was taken in Sonoma County and one in San Francisco.
The Lakeport man was arrested on suspicion of possessing stolen guns. He was taken to Lake County Jail and booked in lieu of $15,000 bail.