The subsidies under the Affordable Care Act are actually tax credits. Let's say I'm single, around 50 years old, I work on commission, I state my income as $17,000 per year, and I receive tax credits of about $500 a month toward my premium. My ship comes in and I make a whopping $50,000, which is over 400 percent of the Federal Poverty Level. And now, guess what? I owe $6,000 back to the IRS since I'm no longer entitled to the tax credits I received.
If I took tax credits I didn't deserve I owe it back. That seems fair, and the IRS will collect those.
By the same token, the Supreme Court may rule that people who received subsidies in states that did not set up state exchanges, which relied on the federal government to set them up, are now not entitled to these tax credits. It seems to me they would also owe the IRS back. Not just for 2014 but for all the tax credits they have received in 2015 as well.