The Supreme Court decided, in a 6-3 decision by Chief Justice Roberts, that federal subsidies are available on exchanges set up by the federal government, despite potentially conflicting statutory language. The Chief Justice's decision was joined by Justices Kennedy, Ginsburg, Breyer, Kagan, and Sotomayor. 

The Chief Justice's majority opinion noted: "Petitioners’ arguments about the plain meaning of Section 36B are strong. But while the meaning of the phrase “an Exchange established by the State under [42 U. S. C. §18031]” may seem plain “when viewed in isolation,” such a reading turns out to be “untenable in light of [the statute] as a whole.” Later, the Chief Justice added:

After telling each State to establish an Exchange, Section 18031 provides that all Exchanges “shall make available qualified health plans to qualified individuals.” 42 U. S. C. §18031(d)(2)(A). Section 18032 then defines the term “qualified individual” in part as an individual who “resides in the State that established the Exchange.” §18032(f)(1)(A). And that’s a problem: If we give the phrase “the State that established the Exchange” its most natural meaning, there would be no “qualified individuals” on Federal Exchanges. But the Act clearly contemplates that there will be qualified individuals on every Exchange. Cite as: 576 U. S. ____ (2015) 11 Opinion of the Court. As we just mentioned, the Act requires all Exchanges to “make available qualified health plans to qualified individuals”—something an Exchange could not do if there were no such individuals. §18031(d)(2)(A). And the Act tells the Exchange, in deciding which health plans to offer, to consider “the interests of qualified individuals . . . in the State or States in which such Exchange operates”—again, something the Exchange could not do if qualified individuals did not exist. §18031(e)(1)(B). This problem arises repeatedly throughout the Act. See, e.g., §18031(b)(2) (allowing a State to create “one Exchange . . . for providing . . . services to both qualified individuals and qualified small employers,” rather than creating separate Exchanges for those two groups).1 These provisions suggest that the Act may not always use the phrase “established by the State” in its most natural sense. Thus, the meaning of that phrase may not be as clear as it appears when read out of context.

The Chief Justice's opinion concluded that, "Congress passed the Affordable Care Act to improve health insurance markets, not to destroy them. If at all possible, we must interpret the Act in a way that is consistent with the former, and avoids the latter. Section 36B can fairly be read consistent with what we see as Congress’s plan, and that is the reading we adopt."

Justice Scalia's dissent, joined by Justices Thomas and Alito, was blistering. The second most senior Justice wrote: 

"Words no longer have meaning if an Exchange that is not established by a State is “established by the State.” It is hard to come up with a clearer way to limit tax credits to state Exchanges than to use the words “established by the State.” And it is hard to come up with a reason to include the words “by the State” other than the purpose of limiting credits to state Exchanges. “[T]he plain, obvious, and rational meaning of a statute is always to be preferred to any curious, narrow, hidden sense that nothing but the exigency of a hard case and the ingenuity and study of an acute and powerful intellect would discover.” Lynch v. Alworth-Stephens Co., 267 U. S. 364, 370 (1925) (internal quotation marks omitted). Under all the usual rules of interpretation, in short, the Government should lose this case. But normal rules of interpretation seem always to yield to the overriding principle of the present Court: The Affordable Care Act must be saved."

In perhaps the most memorable line, he expressed frustration as he wrote "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." 

The decision marks the second decision in three years to uphold the law from a potentially fatal attack. In 2012, the Supreme Court ruled in NFIB v. Sebelius that the individual mandate was constitutional not under the Commerce Clause of the Constitution, but rather as a tax.