The Supreme Court made clear this week that its long push to rein in federal power over states - a federalism movement that could become Chief Justice William H. Rehnquist's legacy - still is far from bedrock principle.
Legal analysts said yesterday that Monday's 6-3 ruling allowing U.S. authorities to prosecute people who use marijuana for medical reasons, regardless of state law, demonstrated how delicate the balance of the court is on questions of states' rights.
A decade ago, the court's five conservative justices were more firmly united in such cases. But more recently, that group has fractured in often unpredictable ways - dismaying some conservatives and leaving the outcome of future states' rights cases uncertain, especially if Rehnquist retires at the end of this term, as many expect.
The next test comes soon and on another high-profile issue: This fall the court will hear a Bush administration challenge to Oregon's first-in-the-nation assisted suicide law.
"Right now, I would say the court is more of a moderate states' right court than an aggressive federalist court," said Jonathan H. Adler, associate director of the Center for Business Law and Regulation at Case Western Reserve University's law school.
"There are four justices who don't like this line of cases generally ... and you have five justices who believe that the courts need to step in and rein in the power of Congress, but their commitment and their understanding of that role varies."
In 1995 and in 2000, the court's five right-of-center members decided two cases that were critical in shifting the court's approach to federalism issues. Ruling in each case that Congress had exceeded its authority over states, the court struck down the Gun-Free School Zones Act and part of the Violence Against Women Act.
In more recent cases, though, the voting lines have shifted. Rehnquist joined a majority opinion that upheld a federal law giving state employees the right to sue under the Family and Medical Leave Act in 2003.
Justice Sandra Day O'Connor cast the swing vote in a 5-4 decision last year that states can be subject to lawsuits under the Americans With Disabilities Act.
This week's case from California produced another surprising split, with Scalia and Kennedy voting against states' rights.
In a sharp dissent, O'Connor called the majority decision "irreconcilable" with the two key cases that shaped the court's federalism position over the past decade.
She quoted from the 1995 gun law case, in which the court said it intended to "protect historic spheres of state sovereignty from excessive federal encroachment."
Responding in his concurring opinion in the marijuana case, Scalia wrote: "I think that criticism is unjustified." Neither of the earlier decisions, he wrote, "involved the power of Congress to exert control over intrastate activities in connection with a more comprehensive scheme of regulation" - such as the Controlled Substance Act.
Roger Pilon, vice president for legal affairs at the right-leaning Cato Institute, criticized the marijuana ruling yesterday as one layered with hypocrisies.
"This is exactly what you get into when you ignore principle and allow politics to trump the law," he said.
"There just is no consistency there - with the possible exception of Thomas. One would have thought there was more consistency on Scalia's part, until yesterday."
Mark V. Tushnet, a constitutional law professor at Georgetown University, countered that Scalia's argument could be defended: "This is one of those things where the law actually may matter," he said. "He develops a very cogent argument."
More broadly, Tushnet said, the current court simply does not have a consistent majority to press states' rights further, and on more substantive issues, than it already has done.
"The Rehnquist court has brought the law of states' rights to the threshold of an open door - but it hasn't stepped through the door," he said.
Which direction the court turns next depends largely on its makeup. Rehnquist, who is 80 and has thyroid cancer, is widely expected to announce his retire- ment when the court finishes its work for the term this month.
That could change the dynamics on federalism questions as early as this fall, when the court is scheduled to hear the Oregon case.
Like the medical marijuana case, the assisted suicide law involves a challenge under the federal controlled substance act and a ruling in favor of states' rights already entered by the San Francisco-based 9th U.S. Circuit Court of Appeals.
"I don't think the cases necessarily rise and fall together," said Case Western's Adler. "The Oregon case is not a slam-dunk, but they're arguing on more stable terrain."
In siding with Oregon officials in a challenge brought by then-Attorney General John Ashcroft, the appellate court said last year that the federal government was trying to "alter the usual constitutional balance between the states and the federal government" - quoting from a 1991 Supreme Court case that gave Ashcroft, then governor of Missouri, his own states' rights victory on the issue of setting a mandatory retirement age for state judges.