Appeals court hears another challenge to health care law

But during almost three hours of oral arguments, the judges asked pointed questions about the so-called individual mandate, which the federal government says is needed to expand coverage to tens of millions of uninsured Americans. With challenges to the law before other federal appeals courts, lawyers expect that its fate will ultimately be decided by the US Supreme Court.

Chief Judge Joel Dubina, who was tapped by President George H.W. Bush, struck early by asking the government’s attorney, “If we uphold the individual mandate in this case, are there any limits on congressional power?’’ Judges Frank Hull and Stanley Marcus, both appointed by President Clinton, echoed Dubina’s concerns later in the hearing.

Acting US Solicitor Neal Katyal sought to ease their concerns by saying the legislative branch can regulate commerce only if it will have a substantial effect on the economy and solve a national, not local, problem. Health care, he said, is unique because of the billions of dollars involved when Americans without coverage seek medical care.

“That’s what stops the slippery slope,’’ he said.

Paul Clement, a former US solicitor representing the states, countered that the federal government should not have the power to compel residents to engage in commercial transactions. “This is the case that crosses the line,’’ he said.

Hull also seemed skeptical about the government’s position that the mandate is crucial to covering the 50 million or so uninsured Americans. She said the rolls of the uninsured could be pared significantly through other parts of the package, including expanded Medicare discounts for some seniors and a change that makes it easier for those with preexisting medical conditions to get coverage.

Hull and Dubina separately asked the lawyers on both sides to focus on a particular outcome: What could happen to the overhaul if the individual mandate were invalidated but the rest of the package were upheld?