The U.S. Supreme Court plunged into debate Monday on the fate of the Obama administration's overhaul of the nation's health-care system, and the justices gave every indication they will not allow an obscure tax law to derail the case. 

A decision is expected by late June, in the midst of a presidential election campaign in which all of U.S. President Barack Obama's Republican challengers oppose the law and promise its repeal if the high court hasn't struck it down in the meantime. 

Arguments over tax law

The first arguments concern whether the challenge is premature under a 19th-century tax law because the insurance requirement doesn't kick in until 2014 and people who remain uninsured wouldn't have to pay a penalty until they file their 2014 income taxes in early 2015. 

Taking this way out of the case would relieve the justices of rendering a decision in political high season, just months before the presidential election. 

— The Associated Press 

With demonstrators chanting outside, eight of the nine justices eagerly jumped into questioning of lawyers about whether the case has been brought prematurely because a 19th-century law bars tax disputes from being heard in the courts before the taxes have been paid. 

Under the new health-care law, taxpayers who don't purchase health insurance would have to report that omission on tax returns for 2014 and would pay a penalty along with federal income tax on returns due by April 2015. Among the issues is whether that penalty is a tax. 

Solicitor General Donald Verrilli Jr., defending the health law, urged the court to decide what he called "the issues of great moment" at the heart of the case. 

'What is the parade of horribles?'

The 26 states and a small business group challenging the law also want the court to go ahead and decide on its constitutionality now. 

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Doctors and medical students supporting the health-care reform law signed by U.S. President Barack Obama gather in front of the Supreme Court in Washington on Monday. (Charles Dharapak/Associated Press)

But one lower court that heard the case, the federal appeals court in Richmond, Va., said the challenge is premature. No justice seemed likely to buy that argument Monday. 

The justices fired two dozen questions in less than a half hour at Washington attorney Robert Long, who was defending the appeals court ruling. 

"What is the parade of horribles?" asked Justice Sonia Sotomayor, if the court decides that penalties are not a tax and the health-care case goes forward? Long suggested it could encourage more challenges to the long-standing system in which the general rule is that taxpayers must pay a disputed tax before they can go to court. 

The questions came so quickly at times that the justices interrupted each other. At one point, Justices Ruth Bader Ginsburg, Elena Kagan and Sotomayor started speaking at the same time. Chief Justice John Roberts, acting as traffic cop, signalled Ginsburg to go first, perhaps in a nod to her seniority. Only Justice Clarence Thomas, as is his custom, stayed out of the fray. 

'Protect my health care'

Attorney General Eric Holder, Health and Human Services Secretary Kathleen Sebelius, Republican Senator Jeff Sessions of Alabama and Florida Attorney General Pam Bondi were in the crowd that filled the courtroom's 400 seats. 

Outside the court building, about 100 supporters of the law walked in a circle holding signs that read, "Protect my healthcare," and chanting, "Care for you, care for me, care for every family." A half-dozen opponents shouted, "We love the Constitution!" 

Republican presidential candidate Rick Santorum was there, too, declaring anew that Republican front-runner Mitt Romney has no standing to challenge Obama on the law since Massachusetts passed a somewhat similar version when Romney was governor. Santorum said, "If you really want Obamacare repealed there's only one person who can make that happen." 

A four-person student band from Howard University was part of the group favouring the law, playing New Orleans-style jazz tunes. 

The law, much of which has still to take effect, would require almost all Americans to obtain health insurance and would extend coverage to more than 30 million people who now lack it. The law would be the largest expansion in the nation's social safety net in more than four decades. 

6 hours of argument time allotted

People hoping for a glimpse of the action had waited in line all weekend for the relatively few seats open to the public. The justices allotted the case six hours of argument time, the most since the mid-1960s.  

Nurses Lauri Lineweaver and Laura Brennaman, who are completing doctoral degrees, had been waiting since noon Sunday and got tickets to see arguments. "It's an honour to be in the court," said Lineweaver, 35. 

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Republican presidential candidate Rick Santorum speaks in front of the Supreme Court in Washington. (Charles Dharapak/Associated Press)

The court will release audio recordings of the arguments on the same day they take place. The first time that happened was when the court heard argument in the Bush vs. Gore case that settled the 2000 presidential election. The last occasion was the argument in the Citizens United case that wound up freeing businesses from long-standing limits on political spending. 

Outside groups filed a record 136 briefs on various aspects of the court case. 

The first arguments Monday concern whether the challenge is premature under a 19th-century tax law because the insurance requirement doesn't kick in until 2014 and people who remain uninsured wouldn't have to pay a penalty until they file their 2014 income taxes in early 2015. 

Taking this way out of the case would relieve the justices of rendering a decision in political high season, just months before the presidential election. 

The biggest issue before the court is Tuesday's argument over the constitutionality of the individual insurance requirement. The states and the National Federation of Independent Business say Congress lacked authority under the Constitution for its unprecedented step of forcing Americans to buy insurance whether they want it or not.