(CN) - An assassination researcher says Dallas police threw him in jail to stop him from selling materials that suggest President John F. Kennedy's death was part of a conspiracy. Robert Groden, who helped force Congress to reopen its investigation of the JFK assassination in the 1976, rents a parking space across from the site of the shooting, where he questions the "lone gunman" theory, according to his complaint in Dallas Federal Court.
Groden says police Sgt. Frank Gorka arrested him in the parking lot near Dealey Plaza on June 13, claiming his booth violated Dallas ordinances that prohibit the sale of literature or films on the JFK assassination.
But Groden claims that the ordinances Gorka cited do not apply to his case, and the permits he was ordered to get do not exist.
Groden says he studied materials from the assassination as an expert for the Select Committee on Assassinations for the House of Representatives.
The self-described "leading critic of the Warrant (sic) Commission" says he wrote five books about JFK's assassination and says he is recognized as "the world's leading expert on the photographic evidence in the JFK case."
The Warren Commission report, published in 1964, concluded that Lee Harvey Oswald, acting alone, fired three shots at President Kennedy from a sixth-floor window of the Texas School Book Depository.
Though the Select Committee on Assassinations did not identify a second gunman, it found that "President John F. Kennedy was probably assassinated as a result of a conspiracy," according to the National Archives.
Groden says while he was working at his table outside of Dealey Plaza, where he sells books, DVDs and other assassination-related materials, police charged him with a Class C misdemeanor, seized his products and took him into custody for almost 9 hours.
Groden claims that Dallas City Hall and the Parks and Recreation Department told him he met all the requirements to operate his business, but Dallas police continue to deny him access.
A few days after being arrested, Groden says he returned to his sales location, but Gorka and Cpl. Rodney Nevils forced him to shut down after just 45 minutes. The officers said they would arrest him if he sold any of his products, according to the complaint.
Groden seeks punitive damages and an injunction, alleging false imprisonment, malicious prosecution and constitutional violations. He is represented by Alex Tandy of Hurst, Texas.