SCOUTUS ruled 5-4 that the Commerce department has the authority to ask the citizenship question, and that the question is not unconstitutional. Roberts’ objection is that the administration didn’t give a good enough justification for it, a patently ridiculous standard. Trump should just declare victory, print the question anyway, and tell SCOTUS to go pound sand.
It isn't the USSC's standard, it's law. See the Administrative Procedure Act.