Kolasky, Deputy Assistant Attorney General, resigned a month after his boss, Assistant Attorney General Charles James, left for energy company ChevronTexaco.
Kolasky will return to Wilmer Cutler & Pickering's partnership in December and will be based at the firm's Washington DC office. James becomes ChevronTexaco's vice-president and general counsel on 9 December.
Kollasky was responsible for the DoJ's international antitrust and policy enforcement. He led the promotion of the worldwide antitrust cooperation and founded the International Competition Network, an informal alliance of 75 competition authorities around the globe.
He rejoins Wilmer Cutler, which he first joined in 1975, becoming a partner in 1979.
James joins ChevronTexaco rather than choosing a return to private practice. He was previously head of Jones Day Reavis & Pogue's antitrust practice.
Both departures come as the Microsoft case finally closes and the DoJ has yet to announce their replacements.