In the case of the Commerce Clause and whether the government can compel people to purchase health insurance the Court is, following the reasoning of Judge Silberman, The Court will look at " four factors in determining whether legislation represents a valid effort to use the Commerce Clause power to regulate activities that substantially affect interstate commerce. I am paraphrasing from the Supreme Court decision to invalidate the Gun-Free School Zones Act of 1990 on the grounds is exceeded the authority of Congress to regulate under the Commerce Clause:
Whether the activity was non-economic as opposed to economic activity; previous cases involved economic activity.
Whether the purchase of insurance is an interstate commerce activity
Whether there had been Congressional findings of an economic link between not purchasing insurance, the economy and/health care costs at any point in time
Whether there is a link between regulated activity or inactivity and interstate commerce. http://en.wikipedia.org/wiki/United_States_v._Lopez
The third factor is the one that Silberman focused on. And like other judges who did so they bought the argument that without a mandate people who didn't have insurance would add costs to the system at some point and therefore not buying coverage is, broadly defined, an economy activity. However, one aspect of the Lopez case not always considered in current discussions. The Court of Appeals that ruled the Gun Free Act unconstitutional found the findings and evidence presented before Congress to justify the passage of the Act pursuant to the federal Commerce Clause power was simply insufficient to uphold the Act. http://en.wikipedia.org/wiki/United_States_v._Lopez#cite_note-9
I don't know if the states bringing suit against the federal government have raised or will raise this argument. I don't know if doing so is a plausible legal strategy. But it would seem pretty easy to poke holes in the claim that the lack of a mandate is responsible for rising health care costs and to argue that the findings and evidence presented by Congress are not enough to support the health care law.
It's probably a point worth pursuing for the following reason: I still believe that whatever the Court decides it won't be to the advantage of the proponents of the law and President Obama in particular. If the Court overturns the mandate the administration has made it clear that the rest of the expansion of government power can go on, as well it can. And if the Court upholds the law, it will re-ignite resentment and then some. Whatever happens, Obamacare will become an important campaign issue, as will it's repeal or wholesale revision. That is as it should be.