Discussing the recent Supreme Court decision on Oregon’s assisted suicide law, the Wall Street Journal editorial entitled Federalism, a la Carte (available for a fee) states:

Supreme Court watchers can be forgiven if they thought they were in a Twilight Zone episode yesterday as they read the 6-3 opinion upholding Oregon’s assisted-suicide law against attempted federal encroachment. The High Court’s liberal wing, joined by Sandra Day O’Connor and Anthony Kennedy, has suddenly discovered the Constitutional virtues of federalism.
Meanwhile, Justices Antonin Scalia and Clarence Thomas, along with Chief Justice John Roberts, argue in favor of the broad grant of federal power that the Attorney General was seeking in Gonzales v. Oregon. Count us with the federalists in this one, even if they are of the born-again variety.
The case concerned the Bush Administration’s attempt to use the 1970 Controlled Substances Act to invalidate an Oregon statute passed in the 1990s that has allowed about 200 state residents to kill themselves with a doctor-assisted barbiturate cocktail. The state’s voters have twice endorsed the statute in referendums. But former Attorney General John Ashcroft tried to block the statute on grounds that the drugs the state allowed to be used for the suicide had been abused under federal law.
Writing for the majority, Justice Kennedy unloads a paean to states’ rights worthy of the folks at the Cato Institute. [See page 6 here.] The federal statute “manifests no intent to regulate the practice of medicine generally,” he writes, and such “silence is understandable given the structure and limitations of federalism, which allow the States ‘great latitude under their police powers to legislate to the protection of the lives, limbs, health, comfort, and quiet of all persons.'”
That sounds good to us, since a policy on assisted suicide is profoundly about health and local police powers. We don’t favor assisted suicide as a policy, especially as evidence has grown about the way it has been abused to become euthanasia in Europe. But in the American system, there’s no good reason that Washington should be able to trump states’ rights in the matter.
…The Court’s majority holds that the federal law in question did not give the Attorney General the authority to determine what constitutes “legitimate medical practice” for the entire country, but was something for the states to decide.
In his characteristically caustic dissent [see page 34 in above link], Justice Scalia zeroes in on the word “legitimate,” and says it is a “naked value judgment” for the Court to decide that somehow the AG lacks such authority because the case involves a practice (suicide) the liberals presumably endorse. And he has a point, insofar as Justice Kennedy’s opinion jumps through logical hoops to square this decision with so many of its previous cases upholding federal power against the states…
In his own brief dissent [see page 59 in above link], Justice Thomas cuts to the heart of the hypocrisy, pointing out that a mere seven months ago five of the six Justices in the majority in Oregon found broad federal authority under the same Controlled Substances Act to forbid the growth of medical marijuana, overruling a California law permitting the practice in Gonzales v. Raich.
Justice Thomas had argued for a more-limited federal authority in Raich, but in Oregon he seems to have cast what amounts to a protest vote for the minority. “I agree with limiting the applications of the CSA in a manner consistent with the principles of federalism and our constitutional structure,” Justice Thomas writes. “But that is now water over the dam.” In other words, he’s not about to join the Court’s liberals in ignoring their own precedents simply to get to their favored policy conclusion.
We sympathize with Justice Thomas’s suggestion that this is another case of results-oriented jurisprudence in federalist drag. But then again, even liberals come to the right conclusion once in a while. And if this case has led them to have greater respect for state prerogatives on profound cultural issues that ought to be settled by voters, rather than judges, so much the better for our democracy.
…Results-oriented jurisprudence isn’t any more admirable from the right than it is from the left.

In a subsequent letter to the editor (also available for a fee), Roger Pilon of the Cato Institute responds to the above reference to the Cato Institute and offers a clarification about the difference between federalism and states’ rights:

In an otherwise excellent editorial commending the Supreme Court for rejecting a federal challenge to Oregon’s Death With Dignity Act…you write that “Justice Kennedy unloads a paean to states’ rights worthy of the folks at the Cato Institute.”
We appreciate the ink, of course, but pause simply to note that “federalism” is not quite the same as “states’ rights.” Rather, it is at bottom about dual sovereignty concerning enumerated and thus limited powers — and hence about pitting power against power for the sake, ideally, of liberty. The sad history surrounding “states’ rights” points to the difficulty often of achieving that ideal. But more often federalism, or dual sovereignty, affords liberties unavailable in a unitary system, as the Oregon case illustrates. Thus, we stand rather less for states’ rights than for federalism, a principle at the heart of the Constitution.

Mark Moller of the Cato Institute offers further commentary on the case, with particular attention to Justice Thomas’ dissenting opinion.