Washington (CNN) -- A 26-state coalition has asked the Supreme Court to decide the constitutionality of the massive health care reform legislation championed by President Barack Obama. The petition filed Wednesday virtually assures a landmark decision by June, in the thick of a presidential election year.
The Justice Department also filed its separate petition Wednesday in the case.
Twenty-six states are challenging the federal law, seeking judicial review of a decision by a federal appeals court in Atlanta this summer, which ruled a key provision of the law to be unconstitutional.
"This case offers this court an ideal vehicle to resolve pressing and persistent constitutional questions arising out of the Patient Protection and Affordable Care Act," said lawyers for the states. "It represents an unprecedented challenge -- involving over half of the states in the nation -- to an unprecedented legislative initiative."
At issue is whether the "individual mandate" section -- requiring nearly all Americans to buy health insurance by 2014 or face financial penalties -- is an improper exercise of federal authority. The states also say that if that linchpin provision is unconstitutional, the entire law with its 450 or so sections must then be scrapped.
Joining Florida in its challenge are Alabama, Alaska, Arizona, Colorado, Georgia, Idaho, Indiana, Iowa, Kansas, Louisiana, Maine, Michigan, Mississippi, Nebraska, Nevada, North Dakota, Ohio, Pennsylvania, South Carolina, South Dakota, Texas, Utah, Washington, Wisconsin and Wyoming.
Virginia and Oklahoma have filed separate challenges, along with other groups and individuals opposed to the law.
The justices now have the discretion to either frame the case around the "severability" question -- whether the individual mandate section can be separated from the rest of the law -- or expand it to include other legal questions raised in the appeals.
The court will probably decide by year's end whether to accept the case. It is almost certain to step in, say legal experts, and oral arguments would be heard early next year, with a decision by late June.
The Justice Department filing was expected. In a statement, the government said, "Throughout history, there have been similar challenges to other landmark legislation such as the Social Security Act, the Civil Rights Act, and the Voting Rights Act, and all of those challenges failed. We believe the challenges to Affordable Care Act -- like the one in the 11th Circuit -- will also ultimately fail and that the Supreme Court will uphold the law."
Two other appeals courts have issued decisions in recent months. One of those cases, from Michigan, has already reached the high court. The other, from Virginia, is expected to be filed in coming weeks.
Those courts have split on the individual mandate's constitutionality, a "circuit split" that all but assures the Supreme Court will decide the matter ultimately.
The case filed Wednesday is led by Florida. "This health care law is an affront on Americans' individual liberty, and we will not allow the federal government to violate our constitutional rights," said the state's attorney general, Pam Bondi. "Our country urgently needs a final ruling from the U.S. Supreme Court."
The states say individuals cannot be forced to buy insurance, a "product" they may neither want nor need.
The coalition of states is asking the court to decide three fundamental questions:
--Whether the entire law must fail because its centerpiece -- the individual mandate -- is unconstitutional.
--Whether states can be forced by the federal government to expand their share of Medicaid costs and administration, with the risk of losing that funding if they refuse.
--Whether state employees can receive a federally mandated level of health insurance coverage.
Among those supporting the states is the National Federation of Independent Business, a small business association. "While the survival of the new health care law remains an open question, small businesses and individuals will continue to face uncertainty and trepidation, hesitant to hire or expand," said Karen Harned, who heads the association's Small Business Legal Center.
There was no immediate reaction from the Obama administration to the new court filing.
The Justice Department had countered the states' argument by saying that since every American will need medical care at some point in their lives, individuals do not "choose" to participate in the health care market. Federal officials cite 2008 figures of $43 billion in uncompensated costs from the millions of uninsured people who receive health services, costs that are shifted to insurance companies and passed on to consumers.
Health care reform, a top Democratic priority since the Truman administration, was passed by the previous Congress in a series of virtually party-line votes. Obama signed the act into law in March 2010. The law is widely considered to be the signature legislative accomplishment of the president's first two years in office.
Among other things, the measure was designed to help millions of uninsured and underinsured Americans receive adequate and affordable health care through a series of government-imposed mandates and subsidies. The federal government stated in court briefs that 45 million Americans last year were without health insurance, roughly 15% of the country's population.
Critics have equated the measure to socialized medicine, fearing that a bloated government bureaucracy would result in higher taxes and diminished health care services.
Opponents derisively labeled the measure "Obamacare." Republican leaders, who captured the House of Representatives in the midterm elections, have vowed to overturn or severely trim the law.
The case is State of Florida v. U.S. Department of Health and Human Services.