Under one scenario, the officials say,  the court could strike down the individual mandate, but uphold the rest of the health-care law. That probably would leave a large number of people without health insurance, which in turn would be likely to cause hospitals and other health-care providers to shift the cost of caring for the uninsured to those that have insurance. 

That could mean increased costs for companies that help pay for their employees' health-care coverage, says Steve Hall, American Council of Engineering Companies vice president of government affairs. Hall says that 99% of engineering firms already provide insurance to their employees.

On the other hand, the court could strike down the entire law, opening the door for Congress to revisit the issue, says Mike Kennedy, Associated General Contractors of America general counsel.

Either way, Kennedy says, “There is a tremendous amount of uncertainty surrounding the law, which is a burden on the economy.”

There is another possible outcome. The justices also said they wanted to address the question of whether the challenge to the Affordable Care Act's minimum-coverage provision is barred by another statute, the Anti-Injunction Act. That law, observers say, blocks a challenge to any federal tax until the levy actually is paid.

If the court determines the penalty for violating the indivual mandate is a tax and the Anti-Injunction Act does bar a challenge, it would amount to punting a decision on the Affordable Care Act's constitutionality down the road.