In voting to uphold the law, the chief justice stuck with a traditional Supreme Court principle that if the justices can find any constitutional grounds on which to uphold a law, they should, says veteran reporter on the court Joan Biskupic.
And Roberts followed his own stated principle of narrowly deciding cases and trying to preserve the integrity of the judiciary in polarized Washington, she says.
One aspect of the ruling would enable states not to cover all of their poor residents through their Medicaid programs.
So states like California, Illinois and Maryland may effectively offer all of their residents health coverage. And states such as Florida and Texas — which have refused to implement the law while they challenged it in court — could reject federal aid, leaving hundreds of thousands of their residents without medical insurance.
Here is an Associated Press Q&A on what the health care law means for you. And here is an AP timeline on the country's century of debate over the role the government should play in helping people afford medical care.