The dispute is over whether the federal government is authorized to provide health-insurance subsidies under HealthCare.gov, the federally run health-insurance exchange, or only under the 14 state-run exchanges.
At stake are subsidies or tax credits granted by the federal government to some five million policyholders in the 36 states that have no state-run exchanges–as well as many more potential buyers of individual policies during the second-year rollout between November 15 and February 15.
The court's ruling could call into question both the mandate requiring mid-sized and large companies to offer insurance to employees or face a fine; as well as the "individual mandate" for most Americans to purchase health insurance by 2015 or similarly face a fine. A decision could be handed down before the current court's season ends next June.