Robert Mueller. Photo: Alex Wong/Getty Images

Special Counsel Robert Mueller has handed off three cases involving U.S. lobbyists who failed to register as foreign agents to the U.S. Attorney’s Office for the Southern District of New York, which is already handling the case against President Trump’s so-called fixer, Michael Cohen.

The cases are related to Mueller’s prosecution of Paul Manafort, Trump’s former campaign chairman who is being tried for alleged financial fraud tied to his work on behalf of political candidates in Ukraine. Manafort pulled in other U.S. lobbyists and attorneys to work on the project, and now U.S. attorneys in Manhattan are looking into whether they violated federal law requiring them to register as foreign lobbyists, and how they were paid.

According to the New York Times, the cases involve former Obama White House counsel Greg Craig, who left the White House to work for the law firm Skadden, Arps, Slate, Meagher & Flom; former GOP Representative Vin Weber, who joined the lobbying firm Mercury Group after leaving Congress; and top D.C. lobbyist Tony Podesta, whose brother John Podesta was the chairman of Hillary Clinton’s 2016 campaign.

The three men have yet to be charged with wrongdoing, and SDNY’s inquiry may not result in criminal charges. CNN notes that it’s unclear if they’re involved in one case, or three separate cases. It’s also not clear why the matter was referred to prosecutors in New York. The men are mostly based in D.C., but SDNY could have jurisdiction if banking transactions occurred in New York. The Washington Post reports that Mueller passed the cases off months ago as he was paring down his caseload.

While failing to register with the Justice Department as a foreign lobbyist carries a penalty of up to five years in prison, it previously hasn’t been strictly enforced. Violators often retroactively register with no serious penalties, but with Manafort and former National Security Adviser Michael Flynn facing charges for not registering, the Justice Department may be changing its approach.