Chief Justice Roberts' opinion in National Federation of Independent Business v. Sebelius upheld the ACA individual mandate as a tax. Disagreeing with the joint dissenters (Alito, Thomas, Kennedy, and Scalia), Roberts, in part III-C of his opinion, demonstrates that the labels used by Congress can not be controlling. (Penalty versus tax.) The "question of the constitutionality of action taken by Congress does not depend on recitals of the power which it undertakes to exercise." (Roberts quoting Woods v. Cloyd W. Miller Co.)
Since this levy is within the Taxing Power, the characterization (label) Congress gives the exaction does not effect to its constitutional status as a tax.
Yet in Part III-D
JUSTICE GINSBURG questions the necessity of rejecting the Government’s commerce power argument, given that §5000A can be upheld under the taxing power. Post, at 37. But the statute reads more naturally as a command to buy insurance than as a tax, and I would uphold it as a command if the Constitution allowed it. It is only because the Commerce Clause does not authorize such a command that it is necessary to reach the taxing power question. And it is only because we have a duty to construe a statute to save it, if fairly possible, that §5000A can be interpreted as a tax. Without deciding the Commerce Clause question, I would find no basis to adopt such a saving construction.
the Chief Justice seems to say that only a strained reading of Congress's "label" and the doctrine of Constitutional Avoidance allow the mandate to be upheld as a tax. Isn't there tension between these two parts of the opinion?