In the majority opinion in today's Supreme Court health care ruling, Chief Justice John Roberts ruled that the law's health insurance mandate is constitutionally valid as a tax, despite the fact that the law itself does not describe the provision as a tax.
In a joint dissent, Justices Kennedy, Alito, Scalia, and Thomas beg to differ:
Our cases establish a clear line between a tax and a penalty: "'[A] tax is an enforced contribution to provide for the support of government; a penalty . . . is an exaction imposed by statute as punishment for an unlawful act.'" In a few cases, this Court has held that a "tax" imposed upon private conduct was so onerous as to be in effect a penalty. But we have never held—never—that a penalty imposed for violation of the law was so trivial as to be in effect a tax. We have never held that any exaction imposed for violation of the law is an exercise of Congress' taxing power—even when the statute calls it a tax, much less when (as here) the statute repeatedly calls it a penalty. When an act "adopt[s] the criteria of wrongdoing" and then imposes a monetary penalty as the "principal consequence on those who transgress its standard," it creates a regulatory penalty, not a tax.
Prior to the Supreme Court, nearly all of the judges who had ruled on the law—even those who deemed it constitutional—agreed that whatever else the mandate might be, it was clearly not a tax.
Chief Justice Roberts and the rest of the majority also managed to rule that the mandate was not a tax, at least for the purposes of the Anti-Injunction Act.