Joining Justice Stevens in the majority were Justices Souter, Ginsburg, Breyer, Kennedy, and Scalia(!) (who wrote his own concurring opinion). In dissent were Justices O’Connor, Rehnquist, and Thomas. Both O’Connor and Thomas wrote dissents. Not (yet) having read all of the opinions, it’s clear Rehnquist dissented because he understands the importance of this case to the Court’s overall federalism jurisprudence. This may explain O’Connor’s vote as well (and, perhaps, Scalia’s concurrence). Justice Stevens has expressed sympathy for medical marijuana in the past, but he and the Court’s other liberals clearly see this case as a chance to narrow the Court’s commerce clause jurisprudence, and it appears they’ve succeeded with help from Kennedy and Scalia.