The Virginia attorney general has promised to file a lawsuit against the federal government claiming that it can't compel Virginians to buy health insurance. His supporters say health care reform violates the 10th Amendment. Does it?
Probably not. The 10th Amendment states that "[t]he powers not delegated to the United States by the Constitution, nor prohibited by it to the states, are reserved to the states respectively, or to the people." The federal government, however, can claim two Constitutional justifications for mandating health care. One is the right to regulate interstate commerce, which includes any business that operates across state lines. (Even if not all health insurance companies operate in more than one state, Congress can still regulate them as long as that regulation is part of a comprehensive interstate scheme, according to the Supreme Court.) Congress also has the Constitutional right to tax. Just as Congress taxes polluting companies for imposing a burden on other people, it could tax Americans who don't buy health insurance for doing the same. As if to emphasize the point, the fine for not buying insurance is levied by the IRS.
With respect to what constitutes "interstate commerce," I was recently told a story of a farmer during the Depression, who was fined by the Government for growing enough of his own wheat, that he could feed his livestock without having to purchase feed grain. The courts ruled that this interfered with his having to engage in interstate commerce through the purchase of wheat from someone else.