Joseph Wayland, a former U.S. Justice Department antitrust official who led significant merger challenges on behalf of the government, has rejoined Simpson Thacher & Bartlett as a litigation partner focusing on complex litigation, antitrust counseling and corporate investigations.

Wayland most recently served as acting antitrust chief for the Justice Department. He joined the department in 2010 as the deputy assistant attorney general for civil enforcement in the Antitrust Division and was named acting head of the division in April. Wayland led the trial team that challenged AT&T’s proposed $39 billion purchase of T-Mobile USA, an ultimately abandoned deal. He also headed the challenge to H&R Block’s proposed merger with TaxAct, a blocked deal.

Wayland first joined Simpson Thacher in 1988 and became a partner in 1994. He said he rejoined the firm because it’s a “great platform for my antitrust and litigation practice.” Wayland said that when he first joined the government, he thought he would stay for 18 months but eventually served for about 26 months, commuting between Washington, D.C., and New York, where his family is based. He noted that it was a better time to leave after the election.