The NRA’s Institute for Legislative Action and its political action committee, the NRA Political Victory Fund, placed $25 million worth of television ads through the same ad-buying executives who also arranged spots for Trump’s campaign.

That ensured that “spending by both the NRA and the Trump campaign would be complementary and advance a unified, coordinated election strategy,” according to the complaint brought by the Campaign Legal Center, which favors greater regulation of money in politics, and the Giffords Law Center to Prevent Gun Violence, a gun safety group.

Federal election law bars campaigns and independent groups from coordinating their spending.

“There is reason to believe that the NRA-ILA and NRA-PVF made illegal, unreported and excessive in-kind contributions to Donald J. Trump for President Inc. in the form of coordinated communications,” according to the complaint. The groups are asking the Federal Election Commission to investigate the matter.

The complaint is the latest in a string of legal challenges to embroil the NRA this year. In April, the NRA said it received donations from about two dozen individuals with Russian addresses. U.S. authorities are investigating whether the gun-rights group funneled Russian money into the 2016 presidential election, McClatchy has reported.

The NRA didn’t respond to a request for comment. The Trump campaign didn’t immediately respond to an email requesting comment.

The complaint cites disclosures that broadcast and cable outlets must file with the Federal Communications Commission when they run political ads. Some forms show that four individuals were buying ads for both the Trump campaign and the NRA at the same stations in the final weeks of the election, listing different employers on different disclosures.

American Media & Advocacy Group bought ads for the Trump campaign, which directed $74.2 million to the firm for that purpose, according to FEC records. The NRA used Red Eagle Media Group, the trade name for a firm called National Media Research, Planning and Placement. The two firms share the same address, according to the complaint, and the same employees.

FEC rules allow campaigns and outside groups to use the same vendor, provided it has procedures in place that create Chinese walls between employees working for each.

“I don’t think we’ve ever seen as much evidence as this of coordination,” said Brandon Fischer, director of federal reform for the Campaign Legal Center. He noted that the four executives are described as senior officials involved in the development of strategies. “Here it’s the exact same employees buying on behalf of the Trump campaign and the NRA.”

Initiating an FEC investigation requires four of the agency’s commissioners to vote to take up the matter. There are currently two Republican commissioners, a Democrat, an independent and two vacancies. Under federal law no more than three commissioners may belong to the same party.

If the FEC doesn’t act, it can be sued in federal court to force it to take action, something Fischer says that his group and the Giffords Law Center could undertake.

Overall, the NRA spent $31.2 million to influence the presidential election, according to the Center for Responsive Politics. The gun rights group ran ads on behalf of Trump in the summer of 2016 at a time when his campaign was silent. The NRA’s ads, which ran in battleground states, attacked Democratic nominee Hillary Clinton for her positions on gun safety as well as her role in the 2012 terrorist attack in Benghazi.