[dragonwriter]

> It was actually a very close ruling (5-4) that hinged on whether "regulating interstate commerce" gave the power to the government to compel people to participate in commerce.

No, it didn't hinge on that point. The court split a number of different ways on different points in the case, but the rationale to which a majority signed on to for finding the individual mandate constitutional was the Taxing Clause, not the Commerce Clause.

There was an apparent 5-4 majority against finding for it under the Commerce Clause (the four conservative dissenters who would have struck it down plus Roberts), though there was no single opinion to that effect joined by any majority.