28 U.S.C. Sec. 455 deals with the disqualification of district court judges and it states in part:
Any justice, judge, or magistrate, of the United States shall disqualify himself/herself in any proceeding in which his/her impartiality might reasonably be questioned.
See also 28 U.S.C. Sec. 144; Code of Judicial Conduct, Canon 3.C(1)(a).
28 C.F.R. Sec. 50.19 establishes procedures to be followed by all government attorneys prior to filing a motion to recuse or disqualify a judge. The regulations require the written approval of the Assistant Attorney General of the appropriate division prior to filing or supporting a motion to recuse or disqualify the judge, justice or magistrate. In cases handled by a United States Attorney's Office, the views and recommendations of the client agency should be submitted with the request for approval.
Approval or denial of such requests will be in writing. Oral authorization will be given, and should only be sought, if the litigation does not allow sufficient time to seek prior written approval. In such cases the attorney in charge of the case is required subsequently to prepare and submit to the Assistant Attorney General a written record fully reflecting that authorization.
[cited in USAM 1-3.000]