Opponents of the Affordable Care Act have been having a fun time trying to scare people with the idea that if the ACA is constitutional, then congress would also be within its rights to mandate that people buy broccoli.
Legal issues aside, I really think these efforts to scare people with the specter of unlimited government founder on the fact that any government empowered to levy excise taxes is conceptually pretty much unlimited. The government is allowed to tax everyone, and use the revenue to subsidize broccoli consumption. Now maybe you think that’s legally distinct from the idea of fining people for failure to consume broccoli. But the practical impact is identical. Whether or not non-eaters of broccoli end up subsidizing broccoli consumption has everything to do with congressional politics and nothing to do with the Supreme Court.
In the specific case of the ACA, the stakes are in fact quite high. That’s because the 111th Congress favored the ACA whereas the 112th congress doesn’t. So if the Supreme Court undoes the law, the votes won’t be there to re-achieve the same thing through a technically different process. But that’s just the same as the case of the broccoli mandate. We don’t have a broccoli mandate because there’s no congressional support for a broccoli mandate. If congress decides to financially penalize people for not eating broccoli (as it currently penalizes people who don’t eat corn) then it will do so and the Supreme Court has no way to stop it. What’s happening now is a quirk of America’s odd legislative process. The votes aren’t there to repeal ACA and the votes aren’t there to pass ACA, so whether or not the court strikes it down is hugely important. That’s an interesting fact about American politics in 2011, but it has implications whatsoever for the conceptual boundaries of congressional power. As ever, the best guarantee that congress won’t do something you don’t like is to win elections.