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Michael Merritt had all but forgotten about the pot bust way back in 1970 when state agents came knocking on the door of his Bakersfield, Calif. home.

The agents, from the state’s Department of Justice, started peppering the 61-year-old avid hunter with questions about the guns he owns. Then they told him to hand them over.

“I didn’t know why they were here,” Merritt told FoxNews.com of the Nov. 5 incident. “Then it hit me in a flash. They were here to take my guns and I didn’t know why.”

Merritt was a convicted felon, according to their records, and therefore not eligible to own the pistols, hunting rifles and various collectibles he had legally purchased and registered. But the idea he was a felon was news to him, Merritt said.

“I kept asking them what the felony was for,” he said. "They just showed me a printout with some code and told me they weren’t sure what it was for.”

It turned out that the outdated felony code on the printout—11910 – was for a pot possession charge which has since been downgraded in California law. Merritt remembered being arrested, and paying a fine -- he thinks it was $100 -- and spending some weekends in the lockup.

“I don’t even remember pleading guilty,” Merritt said. "I probably did. I was young. I was probably scared to go to jail.

"The charge doesn’t exist anymore. It’s a ticket,” he added. “The weird part is that all my weapons were legally purchased with a DOJ background check. I never had a problem.”

“My wife got mad and told them to get out of the house and to not come back without a warrant,” he recalled. “That’s when they got a little angry. They said to her, ‘we’ll come back with a warrant, but he will likely be arrested when we do.”

A bewildered Merritt turned over his guns. He later learned the agents were part of a special state unit tasked with checking the lists of registered gun owners against databases showing people who are not allowed to have weapons. It was set up under a program called the Armed and Prohibited Persons System established in 2001.

The unit falls under the Bureau of Firearms in the state Department of Justice. An assistant chief with the Bureau of Firearms confirmed to local media outlets that Merritt was on the list and showed up as having a felony conviction.

"California has clear laws determining who can possess firearms based on their threat to public safety," California Attorney General Kamala Harris said in 2012. "Enforcing those laws is crucial because we have seen the terrible tragedies that occur when guns are in the wrong hands."

But it turned out that amid all the cross-checking of databases, no one caught that Merritt's pot bust was downgraded to a misdemeanor, making him a legal gun owner. Two weeks later, agents returned and gave Merritt back his weapons.

“They called me and said they were going to return them and that the felony was taken off my record,'" Merritt said.

But the seizure of his guns has left a bitter taste in Merritt's mouth.

“They didn’t even do it the right way,” he said. “They violated my Fourth Amendment rights. The whole thing was upsetting. I was told that I was unable to protect my family. To go hunting, which is something I cherish. I don’t even think I would have been able to vote with the felony charge."