The Chief Justice’s opinion finds an interesting middle ground in the battle of absolutes over the Affordable Care Act. Under the Chief Justice’s opinion, real economic mandates are beyond the power of Congress. Congress can’t force action where there was none. Congress can’t say you must act or else go to jail, for example. The individual mandate is constitutional because despite the name because it’s not really a mandate. Congress called it a mandate, to be sure, but in practice it’s really just a small tax. And the enforcement mechanism is pretty light. So you really don’t have to get health insurance: You just have to pay the smallish penalty if you decide you don’t want it. So Congress lacks the power to say that you go to jail if you don’t buy health insurance. But Congress does have the power to encourage you to get health insurance by imposing a tax if you don’t, as long as the tax isn’t so coercive that it’s really more than just a tax.
Here’s Roberts’ case for why he thinks the distinction is important:
[A]lthough the breadth of Congress’s power to tax is greater than its power to regulate commerce, the taxing power does not give Congress the same degree of control over individual behavior. Once we recognize that Congress may regulate a particular decision under the Commerce Clause, the Federal Government can bring its full weight to bear. Congress may simply command individuals to do as it directs. An individual who disobeys may be subjected to criminal sanctions. Those sanctions can include not only fines and imprisonment, but all the attendant consequences of being branded a criminal: deprivation of otherwise protected civil rights, such as the rightto bear arms or vote in elections; loss of employment opportunities; social stigma; and severe disabilities in othercontroversies, such as custody or immigration disputes.
By contrast, Congress’s authority under the taxing power is limited to requiring an individual to pay money into the Federal Treasury, no more. If a tax is properly paid, the Government has no power to compel or punishindividuals subject to it. We do not make light of the severe burden that taxation—especially taxation motivated by a regulatory purpose—can impose. But imposition of a tax nonetheless leaves an individual with a lawful choice to do or not do a certain act, so long as he is willing to pay a tax levied on that choice.
In other words, the taxing power is a lesser form of regulation that has a lot more in the way of limits: It gives the federal government some power, but not the plenary power granted if the law falls within the Commerce Clause. Of course, you have to pay the tax, and willful failure to pay the tax (that is, knowing you have to but intentionally refusing to pay your tax bill) can be a crime. But you can pay the tax and not get health insurance if that’s what you want. So the “mandate” is just a tax, and it is therefore constitutional.