There was a chance, because of the legal issues in play, that the court might sidestep the entire question, finding the case wasn't ripe for a decision. But many constitutional experts say that is an unlikely outcome since the court heard the case over three days - the longest oral arguments in about 50 years - suggesting that it felt some urgency to rule before the law takes full effect on Jan. 1, 2014.
"There will be a lot of disruption," if the law is found unconstitutional, said Scott Crane, an employee benefits analyst at Tycor Benefit Administrators in Berwyn. "A lot of things that have been implemented may not stick," such as the popular requirement allowing young adults to remain in family coverage through age 26.
The entire health-care industry has been remaking itself since the law's passage. Hospitals have been buying up cardiologists - and each other - to become more efficient. Insurers are preparing to sell policies to individuals through state-run exchanges. And every sector is expecting more insured patients.
The decision brings to a head four years of debate and political conflict that began in the 2008 presidential campaign and exposed two differing visions of the role of the national government. In enacting the Patient Protection and Affordable Care Act, Obama and Capitol Hill Democrats sought to greatly expand health-care coverage through government intervention.
In effect, Republicans, under former President George W. Bush, did much the same thing several years earlier in passing a prescription drug plan for the elderly under Medicare, a $500-plus billion benefit that caused government health costs to soar.
Many of the party's most conservative constituents never supported the prescription drug plan. And when Obama began pushing his proposal for expanding health coverage to millions of uninsured Americans after he took office in 2009, that opposition coalesced into the tea party movement, which helped Republicans retake the House in the 2010 midterm elections.
Public opinion polls show that most Americans oppose the law, but favor individual features such as the coverage of adult children and a ban on excluding people with preexisting conditions from health insurance. And it is likely to be a lightning rod in this year's presidential and congressional races.
Republican presidential candidate Mitt Romney says that if elected, he will work to overturn it as soon as he takes office. Yet, as governor of Massachusetts Romney signed a huge overhaul of health care that required state residents to get health insurance if they hadn't obtained it through an employer. Democrats accuse Romney of hypocrisy on the issue, but Romney responds that state governments have the constitutional authority to enact such measures, while the federal government does not.
If fully implemented, the federal act will have broad effects. About 32 million people will become insured.
But in requiring businesses with 50 or more employees to provide health coverage, the law imposes new and significant costs on employers. If employers covered by the law fail to give coverage, they must then pay a penalty of $2,000 per employee.
By far, the bill's most controversial feature is its requirement that individual Americans buy health coverage or be subject to a penalty levied by the IRS.
The provision was included at the behest of commercial insurers as a way to encourage uninsured Americans who can afford it to buy coverage. The added revenue from those customers is intended to offset the increased costs of expanded coverage and lower rates for people who now cannot get insurance because of preexisting conditions.
Several of the justices were harshly critical of the requirement, called the individual mandate, during oral arguments in March, leading some court observers to speculate that the court would strike it down. If that were to happen, left hanging in the balance would be the rest of the law, which calls for a vast expansion of Medicaid, the government health-care program for the poor, a series of tax hikes to pay for the expansion and many other features.
"Once you take away the mandate, how many more provisions do you take away before the whole thing falls," said Jonathan A. Clark, cochair of the employee benefits practice at the Center City law firm of Pepper Hamilton. "If the whole thing is upheld, that will be clear for clients. If the whole things goes away, that will be the same. If only parts are upheld, that will be the most difficult and challenging option."
If the Supreme Court finds that any one piece of the law is unconstitutional, it must then decide whether the rest survive. This question of "severability," as it is known to constitutional law experts, has undergirded much of the speculation about how the court will rule since oral arguments in March.
In practice, significant portions of the law, such as the huge Medicaid expansion, could function without the insurance mandate, since it would be funded in large part through other savings in the Medicare program projected by the Obama administration.
But the task before the court, according to Carl Tobias, a constitutional law scholar at the University of Richmond, is trying to determine congressional intent: In other words, would Congress have intended for portions of the law to survive, even if other parts were struck down?
Congress occasionally includes a so-called severability clause directing courts to do just that, but it didn't in this case. Yet, courts have partially upheld laws even without such explicit instructions.
"In this context, silence [by Congress] when interpreting an issue doesn't tell you very much," Tobias said. "When there is silence, you really are just guessing."
For some, one of the most notable surprises in the case was the sharp reaction of some justices - Antonin Scalia and Anthony Kennedy - to the individual mandate.
Many legal scholars, like Tobias, felt before the arguments that the court was likely to uphold the individual mandate. They based that view, Tobias said, on a decades-long expansion of federal government power under the constitution's Commerce clause, which gives it the authority to regulate interstate commerce. The Obama administration had cited the Commerce clause in its briefs defending the insurance requirement.
Now, Tobias says, the outcome isn't so clear.
Contact staff writer Chris Mondics at 215-854-5957 or email@example.com.