Didn't the government recently change its stance on this and argue that Congress does have the power to enact this law because it is a tax?
And the answer is: “Yes.”
“The New York Times reports that the Obama administration will defend the ObamaCare mandates as part of its power to tax, despite Barack Obamas contentious debate with George Stephanopoulos when Obama denied it was a tax at all.”
http://hotair.com/archives/2010/07/18/nyt-obama-wh-will-argue-obamacare-mandate-is-a-tax/