The Supreme Court's five conservative justices on Tuesday sharply challenged the Obama administration's arguments for the health-care law, with Justice Anthony Kennedy saying the government has a "very heavy burden of justification" for the law's requirement that people carry health insurance or pay a penalty.
The conservative justices fired a barrage of questions at the government's lawyer, Solicitor General Donald Verrilli, asking him to explain why the Constitution authorizes Congress to enact the insurance mandate.
As in lower courts, the federal government on Tuesday struggled to outline a workable principle that would limit the ability of Congress to require people to make other kinds of purchases in the future. Chief Justice John Roberts said that if the court approved of the mandate, it may be hard to set limits.
"All bets are off," Chief Justice Roberts said.
Justice Kennedy said the mandate would change the relationship between the government and individuals in a "fundamental way," showing skepticism toward Mr. Verrilli's argument that the mandate follows Congress's well-established authority under the Constitution's Commerce Clause.
The court was holding two hours of argument Tuesday morning on the mandate, the centerpiece of the challenge to the Obama health-care law.
Two liberal justices, Ruth Bader Ginsburg and Stephen Breyer, weighed in repeatedly to counter skeptical questions from the court's conservatives.
Justice Ginsburg cited a brief filed to the court suggesting that those who go without health insurance raise costs for other consumers. Health care is different from other products, she suggested, because uninsured people are passing their costs to others.
"When disaster strikes, you may not have the money," Justice Ginsburg said.
Justices Antonin Scalia and Samuel Alito also challenged Mr. Verrilli to explain the limiting principle for the insurance mandate. They asked whether the government could also require people to carry funeral insurance or buy food.
Chief Justice Roberts compared health insurance to fire and police services, which people don't know that they're going to need until an emergency. He asked whether people could be required to carry cellphones to dial 911 faster.
Mr. Verrilli, consistently playing defense, argued that Congress was regulating the health-care market in which people were already participating, rather than breaking new ground by forcing them to buy a product.
Responding to Justice Alito's question about funeral insurance, Mr. Verrilli said that example was "completely different" because if a family can't afford a funeral, the costs aren't shifted to other people.
Justice Alito was the most openly skeptical about the idea that the mandate would stop cost-shifting, wondering if in fact it forces young healthy people "to subsidize services that will be received by somebody else."
In the second half of the session, Chief Justice Roberts and Justice Kennedy asked some questions that suggested a level of sympathy with the Obama administration's defense, while justices Scalia and Alito said hardly anything that could be interpreted as favorable to the government.
Justice Kennedy wavered over the assertion that in health care, a bright line could be drawn between those engaged in commerce and those staying wholly outside the market.
"Most questions in life are matters of degree," Justice Kennedy said. The younger, healthier Americans the law seeks to drive into the risk pool are "uniquely proximate" to affecting insurance rates, he said.
The law's challengers, including a group of 26 Republican-led states, view the insurance requirement as an unprecedented intrusion on individual liberty. They say Congress can't use its interstate-commerce powers to regulate citizens who choose not to participate in the health-insurance market.
The Obama administration argues the insurance mandate is a valid way to address a national crisis in which the uninsured impose huge costs on the U.S. health-care system. It also says the provision is an essential part of the law's insurance overhaul, which require insurers to accept all prospective customers, even if they have pre-existing medical conditions.
Two lawyers representing the challengers were set to respond before the court. Paul Clement, a former solicitor general during the George W. Bush administration, was arguing on behalf of the state challengers. Michael Carvin of the Jones Day law firm was representing the National Federation of Independent Business and a group of individuals challenging the law.
How the court's five-justice conservative majority receives Tuesday's arguments will be crucial to the outcome of the case.