I don’t know how anyone could disagree with Kagan here in good faith. Of course congress has the power to regulate the supreme court. They’ve passed numerous regulations for the court in the past, and the constitution expressly gives the power to regulate the specifics of the court to congress. Even the number of justices in the court is chosen by congress. It wasn’t nine until they passed a bill saying it was. And congress can impeach and remove justices too. I think the more corrupt members of the court just fear any actual oversight happening for once.
And unfortunately even if congress did pass an ethics law and the supreme court self declared they are ignoring it, then the only recourse would be impeachment and removal. I think we all know republicans wouldn’t stand for their federalist society stooges to get booted, so we’re left with the pretty unreasonable prospect of getting 67 seats in the senate controlled by democrats to make that happen. Since republicans are unwilling to enforce any ethics regulations on the court, Democrats would need to keep the presidency, retake the house in 2024, and probably need to end the filibuster to overcome Republican objections unless by some miracle they got up to 60+ seats in the senate, but I still think they should try and pass it. Having supreme court justices flagrantly ignore ethics regulations passed by congress may start to galvanize more support for further reforms.