So when did Obama change from citing the Interstate Commerce clause to say it is a tax? Answer, Obama didn't change his argument. Roberts like an activist judge did in his opinion. Here's an excerpt from last year's Federal court judgment on ObamaCare where it was found to be in violation of Constitution because it was an overreach by Obama stating that the Commerce Clause gave him the authority.
Obama health care overhaul struck down by Pensacola, Florida federal judge
"The central issue remains the constitutionality of the law's core requirement that Americans carry health insurance except in cases of financial hardship. Starting in 2014, those who cannot show they are covered by an employer, government program or their own policy will face fines from the IRS.
Opponents say a federal requirement that individuals obtain a specific service — a costly one in the case of health insurance — is unprecedented and oversteps the authority the Constitution gives Congress to regulate interstate commerce.
Vinson agreed that lawmakers lack the power to penalize citizens for not doing something. He compared the provision to requiring people to eat healthful food.
"Congress could require that people buy and consume broccoli at regular intervals," he wrote, "Not only because the required purchases will positively impact interstate commerce, but also because people who eat healthier tend to be healthier and are thus more productive and put less of a strain on the health care system." ...."
-end snip-
When it was being argued before SCOTUS. Obama himself may not have not been in the courtroom, but it was his directive to claim it was a tax before the court.
I don't like the decision, but it does prove what we have all been saying all along - it is a HUGE tax increase. Thus, the Court today declared Obama and the Democrats in Congress are all LIARS.