You are correct and the Supreme Court has stated just that several times on other type cases (I cannot remember which cases), but Congress cannot set ethics standards for the Supreme Court, e.g. A Justise cannot write a book and sell it.
If I am misrepresenting your statement please excuse me- it is late and I've had a few beers.
No you aren’t misrepresenting me. The constitution does say that Justices serve during “good behavior”, so I infer that Congress could if it wished specify what constitutes “good behavior”. In practice this specification has only occurred by impeachment of behavior considered not good, and the 1804 impeachment of Justice Samuel Chase established a precedent that conviction requires criminal conduct.