Read that article again. Note that it does not say “law” once.
It’s about the canons of ethics. When you become a lawyer, you take an oath to uphold the canons of ethics.
This has been a problem re Justice Thomas for years. The jerk has refused to recuse himself in cases where he clearly should have recused himself. But there’s no teeth to go after him about it, because he’s a SCOTUS Justice.
All of this does not mean “above the law.” It’s a matter of “ethics.”
The American Bar Association controls matters of ethics and doles out disciplinary actions for violations. Not necessarily per any statutes (laws), but per the canons of ethics and ABA rules. This article is saying that there is no disciplinary body that deals with ethics and the SCOTUS. Not ILLEGAL ACTIVITY and the SCOTUS, but ethics.