Back in July, a curious thing happened: Two circuit courts of appeal, both addressing the same issue, released conflicting opinions within hours of each other. In the D.C. Circuit, the panel held that the language of the Affordable Care Act only authorized tax subsidies for low-income individuals who purchased insurance through state exchanges. A few hours later, and a few hours' drive south, the Fourth Circuit went the other way and agreed with the Internal Revenue Service's interpretation, which allows subsidies for those who purchase through the federal exchange.
The D.C. Circuit ruling was a massive blow to the federal program and could have meant the end of Obamacare. Could have, but might not, as the circuit just pulled its opinion and granted en banc review.