Actually, the judicial canons that apply to federal judges do not apply to justices of the Supreme Court of the United States. They are not bound by any particular required code of ethics or rules of ethics, and the only check on a Supreme Court justice is impeachment. No federal Supreme Court justice is ever technically required to recuse herself from any case.

I'm not trying to pick a liberal vs. conservative fight. I'm just pointing out that there is an exception carved out for Supreme Court justices.