A government watchdog group is urging the Federal Election Commission (FEC) in a lawsuit filed on Monday to take action on a complaint against a Swiss billionaire who has funneled money to Democratic causes.

Americans for Public Trust filed the lawsuit in district court in Washington, D.C., alleging the FEC has been slow to act on its May 2021 complaint against Hansjörg Wyss. The watchdog group cited various media interviews and a government filing indicating Wyss is not a U.S. citizen, which would make donating to political candidates or political action committees illegal.

“Americans for Public Trust is suing the FEC for failing to investigate foreign money in our elections,” Caitlin Sutherland executive director of Americans for Public Trust, said in a statement to The Hill. “Mr. Wyss, who is barred from directly or indirectly influencing our elections, has done just that by potentially funneling hundreds of millions of dollars through the Arabella Advisors network to benefit liberal and left-wing causes. Until the FEC takes action, we won’t know the full extent of his foreign interference in our electoral process.”

Americans for Public Trust cited a 2021 Securities and Exchange Commission filing in which Wyss listed his citizenship as a “citizen of Switzerland” as well as a 2021 interview with Swiss news outlet Blick to argue that Wyss can’t donate to U.S. political candidates. The group also cited a 2014 speech in which Wyss said he only carries a Swiss passport, not a U.S. passport or green card.

The lawsuit alleges that Wyss used two nonprofit organizations, the Wyss Foundation and the Berger Action Fund, to contribute millions of dollars to the Sixteen Thirty Fund and the New Venture Fund, two so-called dark money groups that fund liberal causes through operations like The Hub Project and Demand Justice.

The watchdog group is suing the FEC in a push to get the agency, which oversees and enforces campaign finance law, to examine whether Wyss violated federal law with his contributions.

If The Hub Project, for example, ran ads directly targeting federal candidates, Wyss could run afoul of the law by contributing as a foreign national, the lawsuit alleges.

A spokesperson for the Wyss Foundation and Berger Action Fund said in a statement that the two organizations “expressly prohibit their grant recipients from using funding from the organizations to support or oppose political candidates or parties or to engage in partisan voter registration and get out the vote efforts.”

The subject of Wyss’s citizenship and his prolific giving to Democratic causes came into the spotlight last year after he emerged as a potential buyer for Tribune Publishing. He later dropped out of the running to purchase the media company.

He is currently listed as a member of the board of directors at the Center for American Progress, an influential liberal think tank with connections to the Biden administration. Neera Tanden, now a senior adviser to President Biden, previously led the think tank.

Price Floyd, a spokesperson for the Wyss Foundation and Berger Action Fund, told The New York Times in an April 2021 article that Wyss’s donations were intended to boost issues that were important to him.

Updated at 6:23 p.m.