I'm not saying he won't win the case but you're daft if you think it won't be 5-4 on the grounds that congress actually has to pass something to signal their intent to the courts.
The question here is not whether congress has to pass something, the question is can congress delegate this authority which is explicitly set by the constitution.
There were a bunch of sentences regarding non delegation of powers of congress, mainly for federal agencies, and courts deciding that congress can't delegate those faculties, so, by the book, this would be a similar situation. There is actually an ongoing case for this aspect of the discussion:
