A federal judge on Tuesday barred James Cole, a former deputy U.S. attorney general, from continuing to defend the Chinese telecom Huawei, siding with federal prosecutors who argued the Sidley Austin partner should be disqualified based on his role in an unspecified investigation during his tenure at the Justice Department.

U.S. District Judge Ann M. Donnelly’s decision to disqualify Cole came almost six months after federal prosecutors in Brooklyn argued that an “obvious conflict of interest” should prevent him from representing Huawei, which is facing charges it violated sanctions against Iran.