The ACA created a subsidy system for low and some middle income families to help in the purchase of health insurance through insurance exchanges "established by the state". The law sets a cap on the amount of insurance premium that individuals and families will have to pay for the second cheapest Silver plan based upon that person/family's income in relation to the Federal Poverty Level.
States were given the option of establishing their own exchanges or allowing the Health and Human Services Department to run a state marketplace for them. The administration would argue that both types of exchange count as having been "established by the state" (i.e. a state with a federally run exchange having made their choice to "establish" that exchange in their state.) Lawyers will argue day and night on this point, I dare say!
The case turns, I think, on just those four words of the Act: "established by the state".
Plaintiffs attest that subsidies should be available only to people buying coverage on exchanges “established by the state,” i.e. state-run marketplaces. 34 states don’t have their own exchanges. Residents rely on federally run marketplaces - the course opted for by their state representatives. If the court rules in favor of the plaintiffs, subsidies in the form of tax credits would end in those 34 states. Subsidies have made insurance affordable for millions of people who would otherwise have remained uninsured.
The whole point of ACA was to make health care affordable to everybody, not simply to those in states where the state had opted to run their own exchange. If this had not been so, wording would have been clear on this point (or ought to have been!)
There's a somewhat dodgy argument by some lawyers that proposes the real reason for not making the subsidy available in relation to both types of exchange was a way of forcing reluctant states to get on board and establish their own exchanges - or lose availability of subsidies for residents of their state. I can easily imagine that some states would not have wished to get into the exchange/marketplace thing because of the extra worries and risks involved - so much easier to let the government deal with it all! The option and the decision on this did remain with each individual state. States' rights an' all that.
It doesn't seem likely, to me, that there was ever an intention to lock people out of subsidies depending on their type of health exchange. That would have been counterproductive. The aim was to bring in as many insured people as possible, to make the system work as intended.
If SCOTUS finds for the plaintiffs, outlaws subsidies in states with federally run exchanges, the people of those states who become unable to afford health insurance will be rightly incensed. Governors of such states should be under immediate pressure to establish state run exchanges tout de suite! Would they though? Would the people rise up and demand? Would the state representatives comply? Oh.... hmm...and could this possibly be a ploy to force states into running their own exchanges? No, that doesn't feel right....a bit conspiracy-ish for me.
I doubt that those potential eventualities will come about, unless the Justices are feeling particularly obtuse and bloody-minded, with intent to bring down the whole caboodle. Couldn't they have done that on the last opportunity - that time in 2012 when Chief Justice Roberts, for once, saved the day for ACA?(SEE HERE)