28 U.S. Code § 455 - Disqualification of justice, judge, or magistrate judge
(a) Any justice, judge, or magistrate judge of the United States shall disqualify himself in any proceeding in which his impartiality might reasonably be questioned.
(b) He shall also disqualify himself in the following circumstances:
(1) Where he has a personal bias or prejudice concerning a party, or personal knowledge of disputed evidentiary facts concerning the proceeding;
(2) Where in private practice he served as lawyer in the matter in controversy, or a lawyer with whom he previously practiced law served during such association as a lawyer concerning the matter, or the judge or such lawyer has been a material witness concerning it;
(3) Where he has served in governmental employment and in such capacity participated as counsel, adviser or material witness concerning the proceeding or expressed an opinion concerning the merits of the particular case in controversy;
(4) He knows that he, individually or as a fiduciary, or his spouse or minor child residing in his household, has a financial interest in the subject matter in controversy or in a party to the proceeding, or any other interest that could be substantially affected by the outcome of the proceeding;
(5) He or his spouse, or a person within the third degree of relationship to either of them, or the spouse of such a person:
(i) Is a party to the proceeding, or an officer, director, or trustee of a party;
(ii) Is acting as a lawyer in the proceeding;
(iii) Is known by the judge to have an interest that could be substantially affected by the outcome of the proceeding;
(iv) Is to the judge’s knowledge likely to be a material witness in the proceeding.
If Kagan wouldn't recuse herself from the Obamacare case even though she was the Solicitor General in charge of determining the best legal defense for Obamacare, then no one has to recuse themselves ever. You reap what you sow Dems.