The Supreme Court dove into the heart of the health reform law and its most controversial aspect, the individual mandate, in which the federal government had to deliver a stellar case to sway justices of the need to compel Americans to obtain insurance.

Based on pointed questions demonstrating the justices’ skepticism, however, it appeared that Solicitor General Donald Verrilli Jr. struggled to be clear and persuasive about how the healthcare market is different.

During the two hours of presentations, the justices peppered attorneys on both sides with questions, while the attorneys tried to engage the justices to persuade them of their view of the requirement that all Americans obtain health coverage starting in 2014.

[Podcast: Inside the Court: Day 2, the individual mandate hearings.]

Justice Anthony Kennedy set the tone, saying the government “has a heavy burden of justifying” the individual mandate, because it changes the relationship between the government and individuals.

The 26 states led by Florida and the National Federation of Independent Business that challenged the health reform law view the mandate as the federal government encroaching on individual freedom because it forces those who are healthy or do not want insurance to purchase it. The federal government views it as the tool to get most Americans covered so they can have access to healthcare.

At the same time, a large pool of both healthy and not so healthy individuals more broadly spreads the risk of caring for those who are sick, enables healthcare providers to better prevent and manage care among a larger group of people and reduces the use of emergency room services, the costliest care, by those who are uninsured.

While it was difficult to read the justices because they also ask questions as the devil’s advocate, it appeared the government’s case was not as clear and definitive as it could be. Justice Ruth Bader Ginsburg several times reflected back more clearly what the government meant, for instance, comparing the mandate to the creation of Social Security, which was controversial, that all pay into it because “everyone will become aged, disabled or widowed at some time.” 

The justices appeared to question how the healthcare market was different from other markets, such as for cars, which if people don’t buy them will impose an economic burden on others, such as losing their jobs at the plant, or burial services, which can be paid for through insurance but no one is compelled to do so.

Chief Justice John Roberts Jr. also was concerned about the extent of power that Congress could exert in the future to compel people to do all kinds of things “once we accept that everyone is in this market.” Justice Antonin Scalia said impatiently that “Next, they could compel us to exercise.”

Verrilli said that could not happen because the mandate to obtain health insurance is “a means for payment for health care. Health club membership is not.”

“The problem is that 40 million individuals cannot get insurance like the rest of us can,” he said. Those are the individuals who do not have employer-based insurance, Medicare and Medicaid and cannot afford individual insurance or insurers have jacked up prices because of pre-existing conditions.

The states had suggested that could be resolved by using incentives instead of threatening a fine, said Paul Clement, attorney for the states. “If Congress tried incentives, we wouldn’t be here,” he said. Instead, by forcing all Americans to buy insurance, it “upended the Constitution,” he added.

The states also suggested that individuals could buy insurance when they need it, such as at the emergency room.

Verrilli countered in his final argument that that wouldn’t work. “Think how much that would cost at the point of sale. It would be unfathomly high,” he said. Uninsured individuals still receive healthcare at hospitals because the government has mandated it, but the cost shifts to the taxpayer and to those who have insurance through rising premiums, Verrilli said.

[Listen: Oral arguments from Day 2 and from Day 1 of the hearings.]

Kennedy, who is considered one of the justices who could decide either way on the mandate, closed the session with a statement that could indicate a sense of the uniqueness of the healthcare market. “In the insurance and healthcare world, the young person can affect rates that are not present in other markets,” he said. 

While five of the justices were named by Republican presidents and four by Democratic presidents, a 5-4 decision is not a sure thing. According to court watchers, if Kennedy were to side with the mandate, leading to a majority, Roberts might also join the majority, which would enable him to write the majority opinion. 

The Patient Protection and Affordable Care Act (ACA) calls for dramatically increasing the number of Americans who will have access to health insurance. The dueling attorneys are presenting legal arguments for six hours through March 28, and the justices are expected to rule in late June.