One of the most inane restrictions of the ACA in my view, as I noted in my "If I Ran the Zoo" wish list back in 2017, is that it doesn't allow undocumented immigrants to enroll in ACA marketplace health plans ("Qualified Health Plans" or QHPs).
I don't just mean that they aren't eligible for federal financial subsidies--that's a prohibition which I can at least understand, even if I don't agree with it. I mean that they aren't allowed to enroll in ACA exchange-based QHPs even at full price, as noted in Section 1312(f)(3):
(3) Access limited to lawful residents.--If an individual is not, or is not reasonably expected to be for the entire period for which enrollment is sought, a citizen or national of the United States or an alien lawfully present in the United States, the individual shall not be treated as a qualified individual and may not be covered under a qualified health plan in the individual market that is offered through an Exchange.
