Halbig v. Burwell turns on whether or not the IRS can change the words in a law on a whim. The suit arose because the "Affordable Care Act" says federal subsidies flow through ObamaCare "exchanges" when they are set up by individual states.
Some three dozen states did not fall for the offer of federal seed money to start an exchange and the reason for this is simple. States dumb enough to set up their own exchanges would then be responsible for the costs of running their exchange perpetually while refusenik states were liberated from paying the same costs. Also, because of how the law was written, states opting out of state-run exchanges would not see their health insurance markets further distorted by federal subsidies. It was a risk-free way for a state to vote against ObamaCare -- which is both their right in such a circumstance as well as their responsibility in the face of federal overreach.
Both sides in the case agree that if the Plaintiffs win, ObamaCare will be ripped apart. Most states would be exempt from much of the carrot created to sucker people into the dependency of ObamaCare, while their citizens would be forced to pay full price for the stick of ObamaCare's wild federal coverage mandates. Federal representatives of such states would have no leg to stand on to insist their people continue to suffer under ObamaCare because the new subsidy-receiving constituency would no longer exist.
Obamacrats campaigning against the lawsuit are placed in the untenable position of arguing that the language of the law should be ignored because following it would lead to a result that, according to them, would not comport with the purpose of the law as stated in its title, which is of course the "Patient Protection and Affordable Care Act."
The hard truth is ObamaCare does nothing to lower the cost of healthcare, it merely shifts those costs around which actually increases them. Attempting to ignore the language of a law because following it frustrates your administration's imaginary purpose is a truly unique legal argument by a truly unique presidential administration.