Last week, the Supreme Court released a Statement of Ethics Principles and Practices. One of the rationales for not adopting the Conduct of Conduct, in its entirety, concerns recusals.
In regard to recusal, the Justices follow the same general principles and statutory standards as other federal judges, but the application of those principles can differ due to the unique institutional setting of the Court. In some instances the Justices' recusal standards are more restrictive than those in the lower court Code or the statute—for example, concluding that recusal is appropriate where family members served as lead counsel below. A recusal consideration uniquely present for Justices is the impairment of a full court in the event that one or more members withdraws from a case. Lower courts can freely substitute one district or circuit judge for another. The Supreme Court consists of nine Members who always sit together. Thus, Justices have a duty to sit that precludes withdrawal from a case as a matter of convenience or simply to avoid controversy.
I think this reasoning is persuasive, and explains why a different set of recusal rules should apply to the Supreme Court. There are only nine Justices, and the Court should decide cases with all members, where possible.