Actually, he and Cruella have every right to change the RULES, because there are hundreds of references to "...be determined later by the HHS secretary..." in the BILL that Pelosi correctly stated needed to be passed before we would find out what was in it.
The BILL ended up being about 2,000 pages. There have already been 20,000 pages of RULES added since then, and expect at least 20,000 more before it goes live next year - including Obama's "Fix" and the soon-to-come "Un-fix" when he decides to cancel everyone's plans and go to single payer.
Then I would argue that the bill is unconstitutional because Congress cannot cede its law-making powers to the executive branch.