The 26 states and private parties challenging the health care law peppered their briefs with references to Kennedy's writing in the guns case and another decision, from 2010, in which he took a narrower view than the majority of Congress' power to act in an area not spelled out in the Constitution. The court upheld Congress' authority to continue to hold inmates considered "sexually dangerous" even after they completed their prison terms.
At the same time, however, Kennedy said in a concurring opinion in the guns case that "Congress can regulate in the commercial sphere on the assumption that we have a single market and a unified purpose to build a stable national economy." The Obama administration says Kennedy could have been describing health care, which makes up 17 percent of the U.S. economy.
Roberts, on the other hand, joined the majority in the 2010 sex offenders case that broadly endorsed federal power.
As chief justice, Roberts also might feel he has an obligation to try to avoid being in the dissent in a case of such importance.
Ilya Shapiro, a lawyer at the libertarian Cato Institute who opposes the health care law, said that Roberts "as the keeper of institutional integrity, wanting the court to speak with more of one voice" could join with Kennedy and the court's liberal wing, rather than being a dissenter in a 5-4 ruling upholding the law.
Like Roberts, Alito has not had many occasions to weigh in on congressional power. Like Kennedy, he took a narrower view of the 2010 case.
In some ways, Scalia's vote is the most intriguing. He has joined in a series of opinions endorsing limits on Congress' regulatory authority under the Commerce Clause.
Yet the administration is focusing on Scalia's opinion in Raich v. Gonzales, a 2005 case that upheld a federal law banning medical marijuana, even grown and consumed at home, as an appropriate regulation of interstate commerce.
"Congress may regulate even noneconomic local activity if that regulation is a necessary part of a more general economic regulation of interstate commerce," Scalia said in a separate opinion.
Georgetown law professor Randy Barnett, a driving force in the effort to take down the health care law, said he isn't worried about Scalia. "To distinguish his opinion in Raich from this case, Justice Scalia would not even have to break a sweat," Barnett wrote recently.
It's hard to imagine Scalia as the only conservative justice in favor of the law.
If he approved of the law, Scalia would more likely join a significant court majority to ratify it. Administration supporters hope that a larger majority including Scalia would make it harder for Republican politicians to make a partisan case against the law.
Supreme Court: http://www.supremecourt.gov/docket/PPAACA.aspx
EDITOR'S NOTE _ This is part of a weeklong package of stories previewing the Supreme Court's consideration of President Barack Obama's health care overhaul law.
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