Mark Hamer, who served as deputy assistant attorney general and was the second-in-command at the U.S. Justice Department’s Antitrust Division, said on Monday that he is leaving the Trump administration after nearly a year in the post.
In a post on LinkedIn, Hamer noted that when he accepted the position he had committed to working in public service for a year. He characterized 2025 as a landmark period for the division, saying, "The year 2025 was the high-water mark for civil antitrust enforcement, with the largest docket of civil antitrust litigation matters in DOJ’s history."
Hamer added that the division's enforcement actions and probes during that period focused on what he described as high-profile competition concerns in a range of sectors: "technology, healthcare, entertainment, agriculture, real estate and financial services industries," he said.
Prior to joining the Justice Department, Hamer had a long tenure in private practice. He is returning to Baker McKenzie, the law firm where he previously served as global chair of the antitrust and competition practice group.
Hamer took his Department of Justice role last March, stepping in as one of four deputy officials charged with overseeing antitrust work. In that capacity he had responsibility for litigation and civil enforcement matters handled by the Antitrust Division.
Context and role
Hamer was part of the senior leadership team at the Antitrust Division, functioning as the second-in-command and supervising civil enforcement and litigation. His LinkedIn post framed 2025 as an unusually active year for civil antitrust work at DOJ, citing a historically large docket of civil litigation matters.
Transition
The announcement makes clear Hamer will return to private practice at Baker McKenzie, resuming work with the firm where he previously held a firmwide antitrust leadership role. The timing follows a roughly one-year term in government service.
This report is based on Hamer's own public statement and the Justice Department role he held. Details provided here reflect those statements and the official description of his responsibilities.