Delrahim was previously hired as a lobbyist who helped shepherd Google's $3.1 billion acquisition of DoubleClick in 2007. DoubleClick has become a key part of Google's advertising business, which has raised antitrust concerns. "As the technology review progressed, Assistant Attorney General Makan Delrahim revisited potential conflicts with previous work with the Department of Justice's ethics office," a spokesperson said in a statement to CNBC after The New York Times first reported the recusal. "He and the ethics office have decided that he should now recuse himself from a matter within the tech review in an abundance of caution. Associate Deputy Attorney General Ryan Shores will continue to oversee the tech review. Deputy Assistant Attorney General Alex Okuliar, who joined the Antitrust Division last week, will also assist with the tech review." Shores previously worked as in the litigation and antitrust department at law firm Shearman & Sterling.