The Supreme Court of the United States shall consist of a Chief Justice of the United States and eight associate justices, any six of whom shall constitute a quorum.
The Chief Justice counts as a member and he, along with the 8 associate justices equal 9. If three opt out, there is still 6 remaining members which constitutes the quorum necessary to act.
Does the Supreme Court require a quorum to act?
Yes, any 6.
https://www.law.cornell.edu/uscode/text/28/1#:~:text=The%20Supreme%20Court%20of%20the,whom%20shall%20constitute%20a%20quorum.
So if three opt out, they win by default? Lovely.
The Chief Justice counts as a member and he, along with the 8 associate justices equal 9. If three opt out, there is still 6 remaining members which constitutes the quorum necessary to act.