While the D.C. Circuit invalidated the rule by a 2-1 vote, a unanimous 4th Circuit panel upheld the rule, the votes were more complicated.
Judges Edwards (CADC) and Davis (CA4) found the tax credits unambiguously apply to the federal exchange.
Judges Gregory and Thacker (CA4) found the statute ambiguous, and through Chevron step 2, deferred to the IRS.
Judges Griffith and Randolph (CADC) found that the statute unambiguously blocks the tax credits for the federal exchanges.
In a bit of a flashback, Judge Davis was on the CA4 panel that decided Liberty University v. Geithner. He was the only judge who reached the commerce clause issue and found the ACA’s mandate. constitutional on those grounds. Likewise, Judge Edwards was on the D.C. Circuit panel that unanimously upheld the ACA’s mandate.
This is going to be fun with competing cert petitions an en banc petitions. Even if the SG files a petition for rehearing en banc, and opposes the 4th Circuit cert petition, I suspect there are 4 votes on the Court (the NFIB dissenters) who would want to grant cert, before this issue fully percolates.
Update: On a closer read, even Judge Edwards thought the statute was ambiguous, so he should be lumped in with Judges Gregory and Thacker. So 5 out of 6 judges agreed the statute is ambiguous, and does not clearly provide for the tax credits. Three judges had to rely on the uber-deferential Chevron Step 2 to resolve the issue.