INDIANAPOLIS — An influential conservative lawyer leading a lawsuit against Indiana accused the state on Friday of illegally collecting roughly $1 billion in fees from truckers across the country.

Attorney Jim Bopp filed the lawsuit in Indianapolis on behalf of the Small Business in Transportation Coalition, a trucking trade group. Bopp contends Indiana lacks the authority under state law to collect $100 million annually in fees from nearly 400,000 truckers — as it has since 2008 — and distribute them to other states.

Indiana handles registrations and fees on behalf of 41 states under a federally authorized compact that allows interstate truckers to pay fees once a year. The lawsuit says that requires the state to have an agency with the legal authority, resources and personnel to implement the Unified Carrier Registration agreement.

The suit seeks to have all compact-related fees refunded to the truckers.

The Indiana Department of Revenue unlawfully claimed to be that agency, according to the lawsuit.

“The key question is whether the Indiana Department of Revenue was lawfully collecting fees from truckers all over the United States,” Bopp said. “We are convinced that the key legal issue is in our favor.”

Representatives of Republican Gov. Eric Holcomb’s administration declined a request for comment by The Associated Press.

Bopp helped draft the Republican Party platform last year. He’s also the architect of the landmark Citizens United case that opened the door for corporations and unions to make unlimited independent expenditures in U.S. elections.