On a cold night at the northeast end of Stockton, a California Department of Justice agent wearing a bulletproof vest beneath his black uniform knocked on the door of a small tract home. A 65-year-old man living alone peeked out.

The agent started talking as eight other agents stood nearby, unseen by the man. State records showed the man was the registered owner of eight handguns. Separate records showed that twice, authorities deemed that he needed to be held in locked psych wards because he was a danger to himself or others.

The agent's goal was to gain the man's trust and seize his guns. No, the man said, he didn't have the handguns. Yes, the agent and his partners could come in and see for themselves. A half-hour later, they emerged with two revolvers, six bolt-action rifles and a crate filled with 1,000 rounds of ammunition.

"He does have a love of guns," said John Marsh, the special agent in charge of the unit. The man seemed unaware that he had some of the guns, which were stowed in closets and under furniture. Agents didn't arrest him, but would refer the matter to local authorities. "I'd say he is more of a danger to himself. He definitely has his bad days."

As they mull how to overhaul the nation's gun laws, President Barack Obama, Congress and legislators ought to take notice of the work of a unit within the California Justice Department's Bureau of Firearms, the only one of its type in any state in the union.

Night after night, 33 state agents coax guns out of the hands and homes of people who have lost their right to possess them. The program goes by the bureaucratic name of Armed Prohibited Persons System.

Although such a program probably would not have stopped Adam Lanza from massacring 20 first-graders and six educators at Sandy Hook Elementary School last month, the Bureau of Firearms agents undoubtedly have saved lives.

They have seized more than 10,000 owned firearms since 2007, including 2,000 guns last year, almost 120,000 rounds of ammunition and 11,000 illegal high-capacity magazines. Attorney General Kamala Harris said she is trying to figure out how to double the unit's size.

"It's a high priority," Harris said.

The concept is simple enough. Department of Justice analysts compile names of gun buyers based on records of sales dating back to 1996, plus people who registered their assault weapons as a result of a 1989 statute. The list includes 996,000 individuals in California who own 2.2 million guns.

Using other databases, the analysts tease out people who became barred from owning guns after they purchased them. They've been convicted of felonies, violent misdemeanors or criminal domestic violence, or have domestic violence restraining orders against them, or have been detained because of mental illness.

The "armed prohibited persons" list included 19,820 people as of last week, and grows by about 15 people a day. The individuals have registered 38,563 handguns and 1,647 assault weapons. About 30 percent of the people are on the list because of mental illness.

Marsh and his team have gone to some of the most rural parts of the state to seize guns, and have stopped felons returning from Nevada guns shows, where Californians who cannot legally own guns under this state's laws, can buy any kind of gun, no questions asked. The agents recently helped arrest 23 felons in possession of firearms in tough parts of Oakland, seizing 15 handguns, three rifles, three assault weapons and five shotguns.

I tagged along as they knocked on 10 doors on one night in Stockton, and 11 doors in Elk Grove and Sacramento on another night. Marsh said they were slow nights, though agents seized 24 pistols, rifles and shotguns. Abiding by the ground rules, I stayed in Marsh's pickup truck, while agents went about their work.

Their first stop was at the rundown home of a parolee, a Crip, whose new Mercedes sat in the driveway. They searched for man's handgun in his house and car, and came up empty. Marsh described the home as having rodent droppings, cockroaches and two little children. The owner said the gun had been stolen, a common claim.

Some gun owners weren't home, including a man convicted of child exploitation who lived in a gated neighborhood in Elk Grove. Agents would return another night.

At a house in south Sacramento, they learned the target, a convicted child molester, had moved without letting his parole officer know. The current occupants, eight young men, were watching a basketball game and smoking weed. The agents weren't interested in making a pot bust, and left reeking of smoke. They would contact the molester's parole officer the following day.

On the final stop last Tuesday night, after 10 p.m., they knocked on the door of a 39-year-old man who lives on a side street in Del Paso Heights, and had been convicted of assault with a firearm years earlier.

After several minutes, the man opened his door, and they talked their way inside. He had a loaded revolver, a loaded shotgun, and eight other rifles and shotguns, plus ammunition. They took him to Sacramento County jail, where he would be booked on charges of being a felon in possession of guns and ammunition.

He probably won't do prison time. And he could drive to a Nevada gun show to buy more firearms. But Marsh's crew did its part by removing his guns.

"You have the sense you're saving lives," Marsh said. "You're preventing them from killing themselves or someone else."

Treasurer Bill Lockyer, a Democrat, came up with the concept of the Armed Prohibited Persons System in 2001 when he was attorney general. To carry the bill, he turned to then-Senate Republican leader Jim Brulte.

Brulte, who is running to become California Republican Party chairman, was an especially adept lawmaker, and got support from the major interest groups involved in the issue, including the National Rifle Association.

The Legislature approved it without a single "no" vote. The most conservative legislators overlooked the cost, initially $4.3 million a year, though it has grown to $6.4 million. Attitudes since have hardened.

In 2011, Harris pushed legislation authorizing he program to be funded from the $19 fee that people pay when they buy guns. There's little room for compromise on gun control these days. GOP lawmakers at the NRA's request opposed the bill, and the NRA has sued in federal court in Fresno to block the funding.

Harris said the NRA's suit shows it "is spinning out of control." She sent a letter to Vice President Joe Biden last week urging administration support. Rep. Mike Thompson, D-Napa, has become a champion and told me he hopes to free up money to assist states seeking to start similar programs.

Even if the feds do help pay, gun politics are such that some states would refuse the money. The thought of agents picking over lists of gun owners would not be popular in many regions.

Times are different now. But not long ago, Democrats, Republicans, gun control advocates and Second Amendment absolutists devised a program that works. Politicians wanting to curb gun violence would do well to follow the lead of the 33 Bureau of Firearms agents, who night after night knock on the doors of convicts, wife beaters and mentally ill people, and take their guns.

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