A study of insured and uninsured Americans showed that those without health insurance get sicker as they age until they turn 65 and qualify for Medicare, Friday, Dec. 28, 2007. But they're not likely to become as healthy as someone who had health insurance all along. (AP / CBS)

WASHINGTON (July 3, 2012)—The U.S. Supreme Court ruling upholding most of the key elements of the president’s health care law sent a mixed message to the 50 million Americans who don’t have health insurance.

Justices upheld one mandate that affects the uninsured while potentially weakening another one that's just as vital.

The court approved the law's controversial requirement that nearly every U.S. resident carry health insurance or pay a fine, which experts say is essential for guaranteeing affordable coverage in new private insurance markets for middle-class people and small businesses.

But the justices also gave states more leeway to opt out of the law's expansion of Medicaid, the federal-state program for low-income and disabled people.

About half the 30 million uninsured people who are expected to gain coverage through the law would do so through Medicaid, but if states opt out, that could be a problem without an immediately clear solution.