The Supreme Court will hear arguments next Monday to Wednesday over the fate of President Barack Obama's healthcare law, a battle with legal, political and financial implications for the U.S. healthcare system's biggest overhaul in nearly 50 years.

The heart of the arguments will turn on whether Congress exceeded its powers in requiring that Americans obtain insurance by 2014 or pay a penalty, the centerpiece provision in the law revamping the healthcare market, which accounts for nearly 18 percent of the nation's economy.

Here is a chronology of the key events in the legal battle over the law that seeks to provide health insurance to more than 30 million previously uninsured Americans:

March 23, 2010: Obama signed into law the Patient Protection and Affordable Care Act, which Congress approved after a long, bruising political fight. The law, which comes to some 2,700 pages, imposed new obligations on individuals, insurers, employers and states in restructuring the nation's $2.6 trillion healthcare system. The law, which seeks to obtain near-universal coverage and slow down soaring healthcare costs, has become Obama's signature and most controversial domestic policy accomplishment. It has been fiercely opposed by most Republicans. At the White House signing ceremony, Obama said the law embodied "the core principle that everybody should have some basic security when it comes to their health care."

March 23, 2010: Immediately after Obama signed the law, a group of 13 states led by Florida sued to challenge the law's constitutionality, one of a number of lawsuits brought by various parties around the country. The lawsuit, filed in federal court in Florida, was later joined by 13 more states, for a total of 26 of the country's 50 states, and by theNational Federation of Independent Business, which represents small businesses across the country. The states argued the requirement that Americans buy health insurance, a provision known as the individual mandate, exceeded the powers of Congress under the U.S. Constitution to regulate interstate commerce. The states argued the mandate could not be severed or separated from the rest of the law and they also objected to other provisions, saying Congress improperly coerced the states to expand the Medicaid healthcare program for the poor. The state ofVirginia filed its own lawsuit on behalf of its citizens.

January 31, 2011: U.S. District Judge Roger Vinson in Florida ruled for the states and struck down the law as unconstitutional. "Because the individual mandate is unconstitutional and not severable, the entire act must be declared void," he said in his opinion, dealing the Obama administration a major setback. "Regardless of how laudable its attempts may have been to accomplish these goals in passing the act, Congress must operate within the bounds established by the Constitution," wrote Vinson, appointed to the bench by Republican President Ronald Reagan. The Obama administration vowed to appeal to a U.S. appeals court and said it believed the law ultimately would be upheld.

August 12, 2011: The U.S. Court of Appeals for the 11th Circuit, based in Atlanta, ruled by a 2-1 vote that it was unconstitutional to require Americans to buy insurance, siding with the 26 states that challenged the law. It rejected the administration's arguments that Congress could adopt the individual mandate under its powers under the Constitution to regulate interstate commerce or to tax. "This economic mandate represents a wholly novel and potentially unbounded assertion of congressional authority: the ability to compel Americans to purchase an expensive health insurance product they have elected not to buy and make them repurchase that insurance product every month for their entire lives," the majority said in the opinion. The appeals court refused to strike down the rest of the law and it rejected the challenge by the states to the Medicaid provision.

September 28, 2011: The Obama administration, the 26 states and the group representing small independent businesses filed separate appeals with the U.S. Supreme Court. Government attorneys urged the high court to uphold the mandate as constitutional. They argued that Congress had adopted the law to address a crisis in the nation's healthcare market, with millions of uninsured people shifting billions of dollars in costs to others. The states and the National Federation of Independent Business in their appeals argued that the mandate was unconstitutional and that the entire law must fall. The states also argued that Congress acted unconstitutionally by forcing them to expand their Medicaid programs or risk losing federal funding.

November 14, 2011: The Supreme Court announced it would hear the appeals, setting up an expected ruling by the end of June 2012. That would be in the heat of the campaign for the U.S. presidency, which culminates on November 6, 2012. The court could leave in place the entire law, it could strike down the individual insurance mandate or other provisions, it could invalidate the entire law or it could put off a ruling on the mandate until after it takes effect in 2014. A ruling striking down the law would be a huge political and legal defeat for Obama before an election when he will be seeking a second four-year term. A ruling upholding the law would be vindication, but might make healthcare an even bigger political issue for the Republican presidential candidates, all of whom oppose it and want to repeal it.

March 26-28: The Supreme Court has scheduled six hours of oral arguments over three days on the healthcare law, the most time devoted to a single issue in more than 44 years. The last longer argument took place in 1967, when the justices heard eight hours in a case about federal government regulation of natural gas producers and prices, according to records by the Oyez Project at ITT Chicago-Kent College of Law. The main attorneys arguing will be Solicitor General Donald Verrilli, a former White House lawyer who will defend the law; Paul Clement, solicitor general under President George W. Bush, who will be representing the 26 states; and Michael Carvin, a Justice Department official in the Reagan administration, arguing for the small business trade group.

The Supreme Court cases are National Federation of Independent Business v. Sebelius, No. 11-393; U.S. Department of Health and Human Services v. Florida, No. 11-398; and Florida v. Department of Health and Human Services, No. 11-400.

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