Under the mandate, if an individual does not maintain health insurance, the only consequence is that he must make an additional payment to the IRS when he pays his taxes. See § 5000A(b). That, according to the Government, means the mandate can be regarded as establishing a condition—not owning health insurance—that triggers a tax—the required payment to the IRS. Under that theory, the mandate is not a legal command to buy insurance. Rather, it makes going without insurance just another thing the Government taxes, like buying gasoline or earning income. And if the mandate is in effect just a tax hike on certain taxpayers who do not have health insurance, it may be within Congress's constitutional power to tax.

The question is not whether that is the most natural interpretation of the mandate, but only whether it is a “fairly possible” one. Crowell v. Benson, 285 U.S. 22, 62, 52 S.Ct. 285, 76 L.Ed. 598 (1932). As we have explained, “every reasonable construction must be resorted to, in order to save a statute from unconstitutionality.” Hooper v. California, 155 U.S. 648, 657, 15 S.Ct. 207, 39 L.Ed. 297 (1895). The Government asks us to interpret the mandate as imposing a tax, if it would otherwise violate the Constitution. Granting the Act the full measure of deference owed to federal statutes, it can be so read, for the reasons set forth below.

(http://www.autoadmit.com/thread.php?thread_id=1981792&forum_id=2#20977159)