Greg Craig Greg Craig. Photo Credit: Diego M. Radzinschi/ALM

A former top Skadden, Arps, Slate, Meagher & Flom partner has been caught up in special counsel Robert Mueller’s ongoing investigation, as a referral sent to the U.S. Attorney’s Office for the Southern District of New York has resulted in an investigation into possible unregistered foreign lobbying work.

Greg Craig, along with former Minnesota Rep. Vin Weber and lobbyist Tony Podesta, are being looked at by Manhattan federal prosecutors, CNN reported late Tuesday. The referral, however, appears to have been made earlier than its public revelation, based on conversations with sources who requested not to be identified.

Craig left Skadden in April, after he and the firm were in Mueller’s crosshairs in a separate matter. According to reports, Craig managed Alex van der Zwaan, a former attorney in Skadden’s London office, as part of the firm’s work on political matters in Ukraine. Van der Zwaan was charged last year with laundering money, among other things, in connection with his work with former Trump campaign manager Paul Manafort in Ukraine.

Van der Zwaan pleaded guilty to lying to investigators in Mueller’s office in February. Manafort’s trial on a number of related charges opened this week in Virginia.

A spokeswoman for Skadden declined to comment on the referral to the Southern District of New York. A spokesman for the Manhattan U.S. Attorney’s Office also declined to comment.

Patterson Belknap Webb & Tyler partner Harry Sandick, himself a former prosecutor in the Manhattan office, said the referral itself shows that Mueller’s team is acting strategically in what it chooses to prosecute.

“Mueller’s office is sensitive to the limit of the mandate he was given by the deputy attorney general,” Sandick said. “They are trying to make individualized determinations, rather than become what some fear—a prosecutor with an unlimited mandate, answerable to almost no one.”

Sandick noted that the focus on a specific lobbying area has cast a light on a potentially little-known, but consequential, area of legal work. As the prosecution of Manafort and those associated with him has shown, the efforts of lobbyists and campaign workers can “pose a risk to our election system, to our campaigns,” as they connect foreign work back to the United States.

“Manafort really pulls the curtain back on things that are maybe not as widely known as they should be,” Sandick said.

The referral of Craig and the others shows prosecutors in Washington, D.C., and Manhattan are invested in looking into these practices. Craig himself has a long history of work in the political sphere. A former aide to U.S. Sen. Edward Kennedy, Craig would serve as White House counsel to former President Barack Obama. He left the office in 2010 to join Skadden.

Craig could not be reached for comment.