Argument likely will be heard this spring, with a decision handed down before the court recesses for the summer. The justices set aside more than 5 hours of argument on several combined cases.
The White House predicted victory.
A statement by White House Communications Director Dan Pfeiffer said: "Thanks to the Affordable Care Act, 1 million more young Americans have health insurance, women are getting mammograms and preventive services without paying an extra penny out of their own pocket and insurance companies have to spend more of your premiums on healthcare instead of advertising and bonuses. We know the Affordable Care Act is constitutional and are confident the Supreme Court will agree."
The states' petition asks the Supreme Court to resolve several questions, including:
"Does Congress exceed its enumerated powers [in the Constitution] and violate basic principles of federalism when it coerces states into accepting onerous conditions that it could not impose directly by threatening to withhold all federal funding under the single largest grant-in-aid program [Medicaid]? ...
"May Congress treat states no differently from any other employer when imposing invasive mandates? ...
"Does the Affordable Care Act's mandate that virtually every individual obtain health insurance exceed Congress' enumerated powers and, if so, to what extent [if any]) can the mandate be severed from the remainder of the act?"
In its Monday orders list, the court said the states and the Obama administration also should be prepared to argue, "Whether the suit brought by respondents to challenge the minimum coverage provision of the Patient Protection and Affordable Care Act is barred by the Anti-Injunction Act."
The "enumerated powers" question has received the most attention in the lower courts. The challenge by the 26 states was largely sustained in the U.S. appeals court in Atlanta, the only U.S. appeals court to do so. But any Medicaid cutoff is a very serious issue for the states.
Medicaid accounts for more than 40 percent of all federal funds dispersed to states -- $251 billion in 2009 alone -- and approximately 7 percent of all federal spending.
For its part, the Obama administration's petition to the Supreme Court relies secondarily on federal law, but principally cites the commerce clause in Article I of the Constitution.
The requirement that most individuals get health insurance -- those who could afford it -- "is a valid exercise of Congress' commerce power," the government petition said. "It prescribes a rule that governs the manner in which individuals finance their participation in the healthcare market, and it does so through the predominant means of financing in that market -- insurance. It directly addresses the consequences of economic conduct that distorts the interstate markets for healthcare and health insurance -- namely the attempt by millions of Americans to self-insure or rely on the backstop of free care, and the billions of dollars in cost-shifting that conduct produces each year when the uninsured do not pay for the care they inevitably need and receive."
One of the Affordable Care Act cases accepted by the high court, along with the state challenges, came from the National Federation of Independent Business.
NFIB President and CEO Dan Danner said in a statement: "Only 18 months after its passage, the new healthcare law has been brought to the steps of the Supreme Court by America's small-business owners. For the small-business community, this comes not a day too soon. The healthcare law has not lived up to its promises of reducing costs, allowing citizens to keep their coverage or improving a cumbersome system that has long been a burden to small-business owners and employees, alike. The small-business community can now have hope; their voices are going to be heard in the nation's highest court."
The fate of the Affordable Care Act could rest on moderate conservative Justice Anthony Kennedy, with the rest of the court evenly split between four conservatives and four liberals.
There was no indication Monday whether any justice would "recuse" himself or herself -- decline to participate in the case. Some Republicans had called for Justice Elena Kagan to step aside because she was the administration's top courtroom lawyer before joining the high court. Some Democrats had called for Justice Clarence Thomas to stop aside because his wife was connected to organizations dedicated to repealing healthcare reform.