One of the state's largest dealers of synthetic marijuana made good this week on his vow to sue the federal government to make it reveal the legal basis for its high-profile raid on his Duluth store in July, when agents seized a large amount of his inventory, two vehicles and almost $3 million in cash.

Jim Carlson, who said in a 2011 interview that he sells $6 million worth of synthetic marijuana and stimulants annually, filed suit Tuesday in U.S. District Court in Minneapolis.

The suit claims the federal Drug Enforcement Administration and other authorities violated his constitutional rights by seizing his property without stating the legal reason, depriving him of the ability to effectively fight the seizures in court. Federal authorities have yet to charge Carlson with a crime stemming from the raid.

The agents had a search warrant, but the legal basis was sealed by court order, and Carlson seeks to lift that seal.

"We can't even tell what they're claiming violates the law," said his attorney, Randall Tigue of Minneapolis.

Jeanne Cooney, spokeswoman for the U.S. attorney's office in Minneapolis, said her office would respond to Carlson's suit in court filings and had no immediate comment.

July's raid, the second on the store in a year, was part of a nationwide crackdown on what health experts consider the latest illegal drug epidemic: manmade chemicals designed to mimic marijuana, ecstasy and other illegal drugs.

Sold online and in stores as "incense," "bath salts," "plant food" and other products, the drugs have generated thousands of calls to poison control centers and have been linked to more than 20 deaths nationally, including two in Minnesota.

Despite new laws, Carlson has continued selling, saying he's switched to products with different formulas that aren't specifically outlawed.

In addition to asking a federal judge to unseal the search warrant, Carlson's suit asks for an order preventing prosecutors from seeking Carlson's indictment under laws used against other synthetic drug dealers across the country.

The suit argues that the Synthetic Drug Prevention Act of 2012 was not yet in effect when Carlson's store was raided and that the law and other federal statutes used against dealers are unconstitutionally vague.

The suit also claims citizens shouldn't be prosecuted for selling products that the federal government hasn't stopped manufacturers from making or wholesalers from distributing.

Another argument, which Tigue says no other defendant or dealer has made, is that no one should be prosecuted for selling something based on how it causes certain neurons to fire in the brain. Tigue said that defining criminality based on such a brain reaction would make it a "thought crime," and thoughts are protected by the First Amendment.

Larry Oakes • 612-673-1751