Justice Roberts exceeded his authority
If under Marbury v. Madison (5 U.S. 137) the Supreme Court has the authority to review acts of Congress and determine whether they are unconstitutional and therefore void, and the opinion of Obamacare even cited this landmark case by stating "And there can be no question that it is the responsibility of this Court to enforce the limits on federal power by striking down acts of Congress that transgress those limits," how does Chief Justice Roberts and the majority consider this law constitutional knowing that the law, in fact, does exceed the limits on federal power?
By trying to save the law by saying that the "penalty" (the wording of the law) in the mandate, if called a tax, can now be considered constitutional, Roberts exceeded his authority, under the separation of powers, by writing (or in this case) rewriting law.
The issue overlooked in the majority opinion failed to address the limits of the Federal Government control over its people under this law. The big questions for us as United States citizens are (1) does this case overturn Marbury v. Madison since it does transgress Congressional limits and yet was "made" to be constitutional by the majority, and (2) does Congress now have the power to run roughshod over the citizens of this country in express violation of the spirit of the Constitution which the founders intended?