OK, I'll talk about the words even if the concept of meaning has taken a small beating this week.
You know, if they'd said "state exchanges," I could see the argument for ambiguity. That might mean either "an exchange operating in a state" or "an exchange established by a state, as opposed to one established by the feds." How anyone can think "exchange established by a state" is ambiguous in a statute that involves both kinds is really beyond me, particular with evidence that the whole point was to give states an irresistible incentive to set up their own exchanges and not dump the task onto the feds. The states' refusal to set up their own exchanges became a conceivable choice only after the S. Ct. struck down the Medicaid penalty as too coercive, which is the main reason the remaining law now strikes many people as "internally contradictory." That is, it always was a little bizarre that state exchanges would be denied subsidies, but no one paid much attention because they could barely entertain the notion that it would ever happen--and it never would have happened, in all likelihood, until Justice Roberts re-wrote the ACA the first time.
The only way to read "exchange established by a state" as "exchange established by anyone you like" is to demand a certain result and twist the words and standards as necessary. Which is pretty much what the majority opinion announced it was doing: it said the plaintiffs' interpretation was right, but going along with it would be too inconvenient. So the trial court said the language was unambiguous and meant what the White House said. The appellate court said it was ambiguous but meant what the White House said. The Supreme Court said the most obvious reading was that it meant the opposite of what the White House said, but it would be re-interpreted that way anyway because we wish Congress had written something different or at least had employed competent draftsmen.
This doesn't surprise anyone about the liberal judges or even Kennedy. Many of us hoped that Roberts's bizarre "it's a tax/it's a floor wax" approach the last time around was an aberration, but now we see it wasn't, at least not when the stakes are high.
A commenter I appreciate at Megan McArdle's site has been asking people for months now to provide her with an example of improved language that would make "exchange established by a state" unambiguous, if your purpose was to make it clear that exchanges established by the feds would not be eligible for subsidies. She never gets any takers. The most frequent response amounts to "Huh?"
There's been a lot of yelling back and forth about U.S. v. Gore and Heller and Citizens United and whether rightwingers are really consistent about precision of language. I won't for one instant try to argue that you can resolve constitutional disputes without dealing with flexibility and ambiguity in the use of language, especially centuries-old language with a long history and a complicated context. But King v. Burwell was a statutory interpretation case. That's a special animal, where we have precise and useful tools for deciding when the judicial branch should intrude on the legislative branch's prerogatives. The rule is: first the language has to be ambiguous, and only then can you consider the drafters' intent. That's not just my personal opinion of the rule; it's the formulation of the rule confirmed by the majority opinion in King. v. Burwell. If the language is not ambiguous, but the law still stinks and is unworkable, you send it back to Congress for fixing. If Congress has changed its mind in the meantime, tough.
In this case, I personally would have found the drafters' intent a slam-dunk once Gruber shot his mouth off, but let's assume he was lying when he first shot his mouth off and not when he retracted all his previous statements. The fact is, we shouldn't be looking at intent at all, because the argument that the language in question is ambiguous is laughable. Yes, it's "only five words in a 2,000-page bill," but they happen to be the only five words in 2,000 pages that bear directly on the point in dispute. Very, very disappointing, even for someone with no illusions about the Supreme Court consisting of saintly and courageous geniuses.