There are two parts to the decision — the mandate to purchase health insurance and the expansion of Medicaid. Here's the gist of the court's decisions on each:
Mandate: When it goes into full effect in 2014, the health-care law says all Americans (who don't have health insurance through their employers) have to purchase it or pay more on their income tax. The federal government would provide subsidies to make the premiums more affordable.
The Obama administration argued that it had the power to impose this requirement since the Constitution allows the federal government to regulate interstate commerce. The four "liberal" justices agreed with this reasoning. But on this issue Roberts sided with the four conservative justices in ruling that, while the government can regulate economic activity, not buying health insurance is economic inactivity. If that's where it had ended, the health-care law would have been overturned in a 5-4 decision.
Instead, Roberts salvaged it by interpreting the provision as a tax. The government has the power to tax things like buying gasoline or earning income, he wrote, and it can impose a tax for going without health insurance, too.
(It took only a few minutes, of course, for Republicans to start tweeting up a storm: President Obama and the Democrats have imposed the largest middle-class tax in history!)
Medicaid: A substantial part of the Affordable Care Act was the expansion of Medicaid insurance for low-income people — which the states administer while splitting costs with the federal government. The law expanded Medicaid to cover people who make less than 133 percent of the federal poverty guidelines, which is now $20,050 for a family of four. Under the law, the federal government would pick up 90 percent of Medicaid costs, but states that opted out of the expansion would lose a large part of the federal money they currently get for Medicaid.
In Thursday's decision, the court voted 7-2 that the expansion could go forward but that the federal government couldn't penalize states that opt out. So states can choose to refuse help from the federal government to provide coverage to more of their low-income citizens. Gov. Corbett wasn't saying Thursday where he stands on this issue, but providing health care for an estimated 500,000 more Pennsylvanians over five years is a no-brainer.
Thursday's decision doesn't eliminate the very real threat to democracy posed by the U.S. Supreme Court's radical lurch to the right. But for millions of Americans whose access to affordable health care is more secure, it was a day to celebrate.