Additionally, have the courts hashed tax law pretty thoroughly? The Obamacare “tax” isn't really an income (it's not based on income) or an excise tax. As you wrote, it really doesn't seem to fall into any of the existing, constitutional tax schemes.
The Obamacare mandate...er...tax appears unconstitutional, and the SCOTUS can't rule on that until someone has standing, i.e. the tax is actually collected.
Could Roberts be playing the long game, setting up the necessary pieces to go for a checkmate later?
CJ Roberts applied two levels of criteria to decide whether or not the SCOTUS could review Obamacare as a “tax.” Limits imposed by Congress in laws, like the Anti-Injunction Act (AJA), are applied literally. Congress called it a “penalty,” but the AJA specifically applied only to a “tax.” Since it wasn't called a “tax,” the Anti-Injunction Act can't apply.
Constitutional limits, on the other hand, require a much higher level of analysis that cannot be restrained by simple legislative acts or terminology. If the constitution permits taxes on income, for example, anything that's effectively an income tax has to be treated (constitutionally) as such even if Congress calls it something else. I'm not saying CJ Roberts is right, it just appears he believes the constitution cuts to the heart of an issue, while law is taken at face value.
He makes the point it doesn't matter if Congress calls something a penalty if it more accurately fits the description of a tax. Alternately, something isn't a penalty if doesn't met the criteria of a penalty from previous rulings (regardless of what Congress calls it).
The four liberal justices didn't surprise. They ruled the Commerce Clause pretty much lets the federal government do anything. The four conservative justices also didn't surprise. They took Obamacare at face value. If Congress called the mandate a penalty, for example, the four justices treated it as such.
CJ Roberts seems driven by something that doesn't fall into either conservative or liberal definitions (trying to find the right words to describe him). He tried to determine whether the law's effect was constitutional and did not take it at face value like the other justices. That could work for us or against us depending on the case.
I think the mandate could be challenged again on the grounds that it's effectively an income tax (for constitutionality purposes), but it didn't originate in the House. I don't believe that particular issue was addressed. The dissenters treated it as a penalty, and the libs thought it was regulating commerce. Only CJ Roberts seemed keen on making it a tax, and he can't ignore the strict constitutional standards he's applied here if he's consistent.
BTW, Congress could have simply raised taxes and given a rebate for having private health insurance. Wouldn't that be constitutional? I think so. They haven't traditionally assigned tax increases for not doing something, but CJ Roberts is probably right Congress can do nearly anything it wants with income. As we know, The 16th Amendment is pretty broad.