Gregory B. Craig, who served in top counsel positions in both the Clinton and Obama White Houses, has left Skadden, Arps, Slate, Meagher & Flom without explanation.

Craig’s office in Washington said he had retired from the firm where he was of counsel. There was no announcement and his information on the Skadden website was removed.

The firm had no additional information about his departure, and Craig couldn’t be reached.

It’s not clear if his exit was related, but Craig has been publicly connected to recent uncomfortable episodes for the firm involving work connected with Ukraine.

Craig, 73, joined Skadden in January 2010, shortly after leaving the White House counsel job under Obama. He was named head of Skadden’s newly created global policy and litigation strategy practice group.

Craig had worked for 36 years at Williams & Connolly, and also played a key role in Bill Clinton’s impeachment defense in the 1990s.

The Justice Department asked Skadden last year to provide information about work it undertook for Paul Manafort, an embattled former campaign manager for President Donald Trump.

Justice Department officials sought the Skadden-prepared report used by allies of Manafort’s client, Viktor Yanukovych, then president of Ukraine, to justify the jailing of a political rival.

Yanukovych’s government later collapsed and he fled to Russia in 2014. Last fall, Craig was identified by the New York Times as the lead Skadden attorney on the Ukraine work.

The firm also was briefly caught up in special counsel Robert Mueller’s probe into Russian interference in the 2016 election.

Earlier this year, Alex van der Zwaan, who had been a lawyer in Skadden’s London office, pleaded guilty to lying to prosecutors and the FBI about communications involving work performed for the former Ukranian president, who was aligned with Russia.