Gregory Craig has left his role as of counsel in the litigation group at Skadden, Arps, Slate, Meagher & Flom in Washington, D.C., as the firm's ties to Ukraine's former government continue to potentially be of interest to special counsel Robert Mueller III.

Craig, 73, joined Skadden in January 2010 after a year as White House counsel at the beginning of the Obama administration. He was also the lead lawyer behind a controversial report released by the firm in late 2012 about the trial of former Ukrainian Prime Minister Yulia Tymoshenko. Supporters of Tymoshenko, who favored closer ties with the West, claimed her prosecution was politically motivated.

A Skadden employee who answered Craig's phone Tuesday in Washington, D.C., confirmed his retirement from the firm and said she would pass along an interview request. Craig's departure from Skadden—first reported by Above the Law—comes roughly two months after Mueller's team charged former Skadden associate Alex van der Zwaan, the son-in-law of Russian oligarch German Khan, with lying to investigators looking into allegations of Kremlin-backed efforts to influence the 2016 U.S. presidential election.

The charges against van der Zwaan, 33, a Belgian citizen and fluent Russian speaker who worked out of Skadden's London office, renewed scrutiny of the firm's work on behalf of the justice ministry of former Ukrainian President Viktor Yanukovych and his Moscow-friendly Party of Regions. Yanukovych now lives in Russia after being ousted as leader of Ukraine in early 2014 following months of protests in Kiev.

On Monday, federal prosecutors filed an 11-page document in their conspiracy case against President Donald Trump's former campaign manager, Paul Manafort Jr., which contained a reference to a “lobbying scheme” involving the “retention of a United States law firm on behalf of the Ukrainian Ministry of Justice to write a report on the trial of Yulia Tymoshenko,” a leading opposition figure imprisoned during Yanukovych's rule.

Ukrainian hackers who obtained text messages from Manafort's daughter, former Skadden associate Andrea Manafort Shand, last year revealed more information about her father's work for Yanukovych and Skadden's role compiling a 303-page report in 2012 for his government about the circumstances surrounding the arrest and prosecution of Tymoshenko, who was eventually released from prison in early 2014 after Yanukovych's ouster as leader.

According to the document filed Monday by federal prosecutors in the case against Manafort and former Trump campaign aide Rick Gates, who in February agreed to cooperate with Mueller's inquiry, both men used offshore accounts to make payments to the unidentified law firm handling the Tymoshenko report for Yanukovych's government. The document noted that an unnamed public relations firm was hired to “assist in the rollout” of the Tymoshenko report, whose findings were synopsized in a press release that went out on Dec. 13, 2012. Human rights groups and other organizations, such as the U.S. Department of State, criticized the Skadden report at the time for being incomplete and questioned its independence.

Mercury Public Affairs, a government relations firm formed in 2011, has previously been identified in news reports as helping bring aboard Skadden to handle the Tymoshenko report. The federal government's initial indictment of Manafort last fall noted the payment via offshore accounts of $4 million for a Yanukovych-sanctioned report by an unidentified law firm into Tymoshenko's arrest and incarceration.

In its response this week to Manafort's request for a bill of particulars, the U.S. Department of Justice noted that the lobbying scheme on behalf of Yanukovych included a “quotation from a memorandum written by Manafort that briefed the Ukrainian government on the report—the original of which named the law firm and the public relations firm, and was produced to Manafort in discovery as a 'hot doc.'”

Skadden has said previously that it is fully cooperating with Mueller's investigation. Other Skadden lawyers besides Craig listed as signatories on the Tymoshenko report include partners Clifford Sloan and Margaret Krawiec, van der Zwaan and fellow associates Alex Haskell, Allon Kedem and Paul Kerlin.

Craig and van der Zwaan, who was represented by Skadden lawyers during his initial questioning by Mueller's team, have since left the firm, while Kedem is now an assistant in the Justice Department's Office of the Solicitor General.

Cooley litigation partner William Schwartz, a lawyer now representing van der Zwaan, declined to discuss Craig's exit from Skadden. Earlier this month, van der Zwaan received a 30-day jail sentence following his guilty plea in late February to repeatedly making false statements to Mueller's team. He was also ordered to pay a $20,000 fine. In court papers submitted with that guilty plea, van der Zwaan admitted to secretly recording conversations with Gates, Craig and another unidentified individual.

Skadden hired van der Zwaan in 2007, a decade before his marriage to Eva Khan, daughter of German Khan, the Russian billionaire who reportedly sees “The Godfather” films as a “manual for life,” and three years before the firm hired Craig. Before Craig's 11-month stint as White House counsel, he spent roughly 36 years at Williams & Connolly in Washington, D.C., where he was a longtime partner at the storied firm and a former lawyer for President Bill Clinton during his impeachment crisis two decades ago.

As for Skadden, last summer the firm agreed to refund some $567,000 in attorney fees to Ukraine's current government, which is led by President Petro Poroshenko, a pro-Western leader who has been criticized in recent months for setting aside anti-corruption initiatives. Ukrainian government records compiled by Yanukovych's regime had stated that Skadden was paid a mere $12,000, a sum beneath the level required in Ukraine for an open bidding or procurement process, for its work on the Tymoshenko report.