It seems to me the key to interpreting the Affordable Care Act subsidies to the states that use the federal exchange is the meaning of the word “established”. The states that have their own exchange and the federal system were in fact not built by states or the federal government – they were contracted out to programming companies who actually built them. Some states may have used the same companies as the federal government did. Those States did not build hospitals or health care companies or train doctors to work in the system. They used already established systems.
So if a State uses the federal system but puts in local health care companies, or in any legislative way or administrative way affirms the choice of the federal exchange, they have actually “established” the federal exchange as the exchange for the State.
The Supreme Court loves to point out words who’s use is not clearly explained in legislation. Hence, they have to accept the broad interpretation of the word “established” in the ACA.