The 11th Circuit, in a 2-1 decision, has struck down the individual mandate of the Affordable Care Act (it upheld the rest of the act, reversing the lower court decision striking it down in total). This represents the first appellate court to strike down (part of) the law, and it also evens the tally of judges "crossing party lines" -- Judge Hull, part of the majority in this case, was appointed by President Clinton (the 6th Circuit decision upholding the law was authored by conservative rising star Jeffrey Sutton).
I've only skimmed the majority and dissent (the opinions, in total, run over 300 pages). But it is notable that the majority couldn't bring itself to embrace the fabled activity/inactivity distinction -- at least not directly. Instead, it seems to rely on a vague pastiche of constitutional red-flags (as the opinion puts it "indicia of constitutional infirmity"), including the mandate's "unprecedented" nature, the status of health care as a traditional state function, and the inactivity problem which appears to flit, ghost-like, in and out the majority opinion.
Faced with such an amorphous majority opinion, Judge Marcus wrote a dissent that is, in my opinion, sterling. In part, I think that's simply because it is easier to write a dissent than a majority opinion. It's easier to attack than defend, easier to break down than build up, easier to negate than affirm. The majority's struggle to simultaneously strike down the law while circumscribing their decision is indicative of this slant. Still, it's ironic that a high-profile dissenting opinion might represent the most aggressive and persuasive defense of the ACA in the judiciary today.
Judge Marcus hits the critical points, which are (a) that the case against the ACA entails a dramatic shift in Commerce Clause jurisprudence that has not yet been hinted in Supreme Court jurisprudence, (b) that many of the objections against the ACA are based not on infirmities with the law itself, but rather vague gestures towards a "slippery slope" which don't take into account the constitutional limits on the commerce power that actually already exist, and (c) the tendency of anti-ACA advocates to demand the courts act as "super-legislatures", using the blunt hammer of judicial review to strike down laws on basis of technical objections to their scope and structure. He also observes that, without relying on the supposed activity/inactivity distinction, the majority never in fact clearly states what the constitutional problem with the law actually is.