I took just a few moments to scan the Summary section of the lawsuit and found the opening and closing paragraphs of interest.
From the opening paragraph:
As statutory construction cases go, this one is extraordinarily straightforward. There is no legitimate way to construe the phrase “an Exchange established by the State under section 1311” to include one “established by HHS under section 1321.” Congress expressly contemplated both state established Exchanges (in the first instance) and HHS-established Exchanges (if states refused to establish their own); because it specifically singled out for subsidies one type, and only one type, courts must give effect to that plain language.
From the closing paragraph:
If the rule of law means anything, it is that text is not infinitely malleable, and that agencies must follow the law as written—not revise it to “better” achieve what they assume to have been Congress’s purposes. This case may be socially consequential and politically sensitive, but that only heightens the importance of judicial fidelity to the rule of law and well-established interpretive principles. Under those principles, it is clear that the IRS Rule must fall. (emphasis added)
It comes down to “do words mean things.” Unfortunately, in this day and age, it appears that words ARE becoming infinitely malleable.