Five Justices Rejected the Government's Commerce Clause Theory. Does that Count as a Legal Precedent?

While Chief Justice John Roberts sided with the Supreme Court's liberals today in order to uphold ObamaCare's health insurance mandate under Congress' power to "lay and collect Taxes," Roberts also sided with the Court's conservatives in rejecting the Obama administration's sweeping argument that the individual mandate was permitted under Congress' power "to regulate commerce…among the several states."

Does the Commerce Clause portion of today's ruling count as a binding precedent? It might. As Georgetown law professor Lawrence Solum points out at his Legal Theory Blog, the part of Roberts' opinion which describes why the individual mandate may be described as a tax "suggests that this characterization was influence by the fact that this characterization was necessary to uphold the mandate (and hence perhaps the entire ACA as constitutional)." In other words, when federal judges turn to Roberts' ruling in the future, they may be required to take his description of the Commerce Clause and its limits into account.

As textual evidence for this reading, Solum points to the following passage from Roberts, which "might be read as signalling that the Commerce Clause discussion was necessary to the logic of the opinion." Here's Roberts:

Because the Commerce Clause does not support the individual mandate, it is necessary to turn to the Government's second argument:  that the mandate may be upheld as within Congress's enumerated power to "lay and collect Taxes.

That does sound like Roberts' Tax Clause argument cannot be divorced from his Commerce Clause argument. I'd also add that Roberts makes the point even more explicit when responding to Justice Ruth Bader Ginsburg's sharp attacks on his "crabbed reading" of the commerce power:

JUSTICE GINSBURG questions the necessity of rejecting the Government's commerce power argument, given that §5000A can be upheld under the taxing power. But the statute reads more naturally as a command to buy insurance than as a tax, and I would uphold it as a command if the Constitution allowed it.  It is only because the Commerce Clause does not authorize such a command that it is necessary to reach the taxing power question. And it is only because we have a duty to construe a statute to save it, if fairly possible, that §5000A can be interpreted as a tax.  Without deciding the Commerce Clause question, I would find no basis to adopt such a saving construction.

So the upshot is that Roberts' powerful dismissal of the government's unprecedented Commerce Clause theory may end up binding lower court judges and serving as precedent for future Supreme Court cases.