What's surprising about this opinion is that the majority opinion is done in a way we're not used to seeing from Roberts: It is, as far as I can see, apolitical. His own dislike of the statute leaks through in places, as does his disdain for Congress. (So, for example, Roberts refers at one point to the "complicated budget procedure known as reconciliation" through which the ACA was passed, noting that it thus "bypassed the Senate's normal 60-vote filibuster requirement," assuming the Obama-era dysfunction in which every bill was filibustered represents a new but permanent normal.) Still, I agree with Garrett Epps: this is, at least as far as can be seen, John Roberts calling balls and strikes, as he promised to do in his confirmation hearings, not wildly distorting precedents or overruling decades of settled law, as I have previously pointed out. He didn't defer to the IRS, for example, which could have left the door open to a new interpretation under a new administration. No, this was straight up Statutory Construction 101: Read the statute--the whole statute, in context. If there's an ambiguity as to what exchanges were meant, look to the stated purposes of the statute, and be guided by that in selecting the two alternatives.
Now, the dissenting troika of Scalia, Thomas and Alito, would have the reader believe that the one phrase that has been bandied about so much, referring to an "exchange established by a State" was itself dispositive, and that no subsidies were available to those who received their benefits from a federally established exchange.
Well, clearly so. The ACA did not create a fallback for federal intervention of a state declined to create an exchange. Who could think such a thing? Oh, how about Scalia, Thomas, Kennedy (who was in the majority this time) and Alito, in their Scalia-penned dissent in NFIB v. Sebelius (2012):
If Congress had thought that States might actually refuse to go along with the expansion of Medicaid, Congress would surely have devised a backup scheme so that the most vulnerable groups in our society, those previously eligible for Medicaid, would not be left out in the cold. But nowhere in the over 900-page Act is such a scheme to be found. By contrast, because Congress thought that some States might decline federal funding for the operation of a “health benefit exchange,” Congress provided a backup scheme; if a State declines to participate in the operation of an exchange, the Federal Government will step in and operate an exchange in that State. See 42 U. S. C. §18041(c)(1).Sebelius (Dissent of Scalia, J.) at sec. IV (E)(2) (emphasis added).
So what changed in three years?
Well, I admit I was unduly suspicious about the outcome, but I predicted that Scalia, Thomas, and Alito would not follow their previous reading of the exact same language in NFIB v. Sebelius. Only Kennedy did follow his own prior interpretation of the statute, and thus joined the majority. Scalia and his fellow dissenters not only reversed their own prior interpretation of the text (rejecting arguments to the contrary summarily as "applesauce"), they excoriated anyone who could read it as they did back then, accusing the majority of "chang[ing] the usual rules of statutory interpretation for the sake of the Affordable Care Act. That, alas, is not a novelty." Scalia then goes on to state that
Having transformed two major parts of the law, the Court today has turned its attention to a third. The Act that Congress passed makes tax credits available only on an “Exchange established by the State.” This Court, however, concludes that this limitation would prevent the rest of the Act from working as well as hoped. So it rewrites the law to make tax credits available everywhere. We should start calling this law SCOTUScare.An argument that would have been much more credible had Scalia himself not described the language at issue consistently with the majority opinion's reading of it today, a bare three years ago. His bitter quip about "SCOTUScare" suggest his own agenda: ScaliaCare means that statutory provisions mean whatever it takes for Obama to lose any case before the Supreme Court.