Six cases involving President Barack Obama's healthcare overhaul legislation are pending before the Supreme Court as part of the legal battle over the law's fate.
The following key issues have emerged in the legal briefs recently filed in the cases stemming from Obama's signature and most controversial domestic achievement that involved the biggest reform of the healthcare system in nearly 50 years:
INDIVIDUAL INSURANCE MANDATE
The most important issue involved whether the Congress exceeded its power by requiring that all Americans buy health insurance or pay a penalty. The law aims to provide more than 30 million uninsured Americans with coverage.
The Obama administration in its Supreme Court appeal argued that Congress could enact this provision, called the individual mandate, under its powers in the U.S. Constitution to regulate interstate commerce. The mandate is due to take effect in 2014.
Congress adopted the law to address a national crisis of health insurance costs rising beyond the reach of millions of Americans and coverage denied to millions more, Solicitor General Donald Verrilli, a former White House lawyer, said in a brief.
Opponents of the law, including 26 of the 50 states, argued that Congress exceeded its powers. They said the law dramatically expanded the federal government's power and argued that the provision should be struck down as unconstitutional.
Former Bush administration Solicitor General Paul Clement, who represents the states, called the law "an unprecedented legislative initiative" that seeks "to force individuals to engage in commerce so that the federal government may regulate them."
WHAT HAPPENS TO THE REST OF THE LAW?
In a broader issue, the states and the National Federation of Independent Business -- a lobbying group for small businesses -- said the entire healthcare law must fall if the mandate is declared unconstitutional.
The federation and states contend that the individual mandate is at the heart of the law, a carefully crafted compromise, and new insurance regulations and other provisions cannot survive on their own.
The administration disagreed. It said it would be wrong to strike down all other provisions of the law, especially those unrelated to the mandate, such as the requirement that insurers provide coverage for young adults.
The administration said a few key provisions, including one that will bar insurers from refusing to issue coverage to a person because of a pre-existing medical condition, could not be separated from the mandate.
EXPANSION OF MEDICAID ON THE STATES
The states also challenged the expansion of Medicaid, a federal-state partnership that provides health care to poor Americans. They argued that Congress unconstitutionally forced the expansion on the states by threatening to withhold billions of dollars in funds from states that refuse to cooperate.
The administration said the provision expanding Medicaid eligibility to cover individuals with income up to 133 percent of the federal poverty level was a valid exercise of Congress's power to set the terms in appropriating federal funds.
MUST THE PENALTY BE IMPOSED FIRST?
The Obama administration and some opponents of the law asked the court to address whether lawsuits challenging the mandate are barred because the penalty for not obtaining individual insurance has yet to be imposed.
At issue is a federal law aimed at preventing lawsuits from tying up tax collection and whether the challenges can only be decided after taxpayers actually begin paying the penalty for not purchasing insurance.
The administration said the law, the Anti-Injunction Act, did not require dismissal of the challenges to the mandate. But the administration said the Supreme Court should consider the issue and consider appointing a lawyer to make that argument.
ARGUMENTS LIKELY IN MARCH
The Supreme Court next month is expected to consider the various appeals, to officially agree to take up the law, and it could clarify the issues to be decided.
The next steps would be for legal briefs to be filed, the scheduling of oral arguments, most likely in late March, and a ruling expected by the end of June.
Legal experts said it was impossible to predict how the court might rule. A decision by the nine-member court, closely divided with five conservatives and four liberals, could come down to Chief Justice John Roberts and Justice Anthony Kennedy, who often casts the decisive vote, they said.
The Supreme Court cases are Thomas More Law Center v. Barack Obama, No. 11-117; National Federation of Independent Business v. Sebelius, No. 11-393; U.S. Department of Health and Human Services v. Florida, No. 11-398; Florida v. Department of Health and Human Services, No. 11-400; Virginia v. Sebelius, No. 11-420; and Liberty University v. Geithner, No. 11-438.