A 46-year-old Stillwater man found with a trove of homemade explosives and hundreds of rounds of high-powered ammunition is part of an anti-government movement and claimed to authorities that he was not subject to certain criminal laws, according to the FBI.

Wayne Robert Lund, indicted by a grand jury on multiple weapons charges this week, also claimed that the explosive devices found in his car and in subsequent searches elsewhere were used for his hobby of setting off rockets in western Wisconsin.

Lund has been in custody since Oak Park Heights police arrested him near the Wisconsin border last month upon discovering that his driver's license had been revoked and his vehicle registration was expired. Since then, according to newly unsealed federal criminal charges, state and federal law enforcement have uncovered numerous small homemade explosives called "cricket bombs," more than 800 rounds of high-velocity ammunition and documents affiliated with a Minnesota chapter of the so-called sovereign citizen movement.

Lund, whose criminal history includes felony terroristic threats and DWI convictions, is barred from possessing ammunition or explosive devices. A federal grand jury charged Lund last week with possessing unregistered firearms and additional counts of being a felon in possession of explosives, firearms and ammunition.

According to a newly unsealed affidavit written by an FBI special agent on the Joint Terrorism Task Force in Minnesota, Lund had seven "cricket bombs" and a PVC pipe with caps screwed on both sides when he was stopped on his way to Wisconsin on Nov. 2. "Cricket bombs" are a term used by law enforcement to describe the CO2 cartridges that Lund filled with explosive material. In an interview with investigators, Lund said he was not aware of the term and said the devices were used to launch hobby rockets. The PVC pipe was later found to contain black-colored powder and shards of a material that resembled broken glass, according to the charges.

FBI bomb technicians confirmed that the cricket bombs were CO2 cartridges packed with explosive material that creates an "overpressure effect" when ignited, "causing all the blast pressure from inside the container to be forced out." Special Agent Erinn Tobin, who wrote the affidavit for Lund's federal criminal complaint, compared that technique to the pressure cooker bombs deployed during the 2013 Boston Marathon bombing.

Lund told investigators that he had no intention of hurting anyone or damaging property. He said he does not research anything about his rockets online and instead learns by experimenting on his own. Lund denied that he designed anything to be a "destructive device." He said he works with a friend in Houlton, Wis., to make their own black powder out of potassium and put it inside metal CO2 cartridges, and that the two buy their wicks from firework stands.

Between additional searches of Lund's vehicle and a hotel room where he had been staying, police found additional CO2 cartridges, shotgun primers, and hundreds of rounds of ammunition that law enforcement described as capable of penetrating standard body armor.

According to charges, investigators also retrieved multiple documents related to the so-called sovereign citizen movement. People claiming that designation have unsuccessfully attempted to say they are immune from state and federal laws, including paying taxes.

Lund declared that he is an "American National," and was covered under the "law of the land."

According to the complaint, when told by the investigator that he was barred from possessing ammunition as a felon, Lund replied: "Oh, no. There's a little difference to that. There's a difference between the public and the private. I did my certificate of assumed name, which separates me from the public and private side of things."

Tobin wrote that she interpreted this exchange as Lund saying that because he claims to be a sovereign citizen — or "private" — he is exempt from criminal law if he is not planning to harm anyone. She added that many self-proclaimed sovereign citizens believe they are not subject to any federal laws or jurisdictions within the United States, a claim that has regularly failed in court.

"American Nationals believe that they can declare themselves sovereign, or private parties, and no longer be subjected to the rules and laws of the U.S. government," Tobin wrote. "This extends to the belief that sovereign citizens or 'privates' do not have to obey criminal laws."

Tobin wrote that she was aware of several cases in which individuals espousing the sovereign citizen ideology have committed or attempted to commit domestic violent extremism to further this ideology.

Lund made his first federal court appearance this week in Minneapolis. U.S. Magistrate Judge Dulce Foster ordered that Lund remain detained pending a Dec. 16 detention and arraignment hearing. A federal defender listed as representing Lund did not return a message seeking comment.