In the majority opinion, Chief Justice John G. Roberts Jr. wrote that the 2010 health-care statute's “individual mandate” provision, which requires that Americans obtain health insurance by 2014 or pay a tax penalty, is constitutional. The mandate was the centerpiece of the law, and the court’s decision on that issue upholds most of the statute.

The court did reject one provision, the law’s Medicaid expansion, which would deny federal Medicaid funds to states that choose not to expand their coverage to all individuals under the age of 65 who live below the poverty line.

The high court's decision was deeply disappointing to construction-industry and other business groups, which contend that the health-care law poses problems for employers.

The Associated Builders and Contractors' 2012 national chairman, Eric Regelin, said, "Under this law, employers have seen insurance premiums increase; have had their plans discontinued, forcing some to purchase more expensive policies; or have had to drop their coverage altogether." Regelin is president of Granix LLC, Ellicott City, Md.

The high court's majority was narrow, and Roberts' vote proved pivotal. The chief justice, joined by Associate Justices Ruth Bader Ginsburg, Stephen G. Breyer, Sonia Sotomayor and Elena Kagan, said the individual mandate provision can be viewed as a tax and is therefore constitutional. Writing for the majority, Roberts said, "Because the Constitution permits such a tax, it is not our role to forbid it, or to pass upon its wisdom or fairness."

Roberts rejected the government’s argument that the law is permissible under the Constitution’s Commerce Clause. He wrote, "The Federal government does not have the power to order people to buy health insurance. … The Federal government does have the power to impose a tax on those without health insurance."

Reaction to the decision was swift and divided. President Obama said, “The highest court in the land has now spoken. We will continue to implement this law. And we'll work together to improve on it where we can. But what we won’t do—what the country can’t afford to do—is re-fight the political battles of two years ago or go back to the way things were."

But House Republican leaders are seeking to do just that. House Majority Leader Eric Cantor (R-Va.) called the ruling a “crushing blow to patients throughout the country” and said he has scheduled a July 11 floor vote on repealing the health-care law. House Speaker John Boehner (R-Ohio) told reporters, "The real outcome of today's decision is to strengthen our resolve to make sure that this law is, in fact, repealed."

But the Democrat-controlled Senate is not likely to approve a repeal bill this year. Even so, the health-care law is likely to be a key election-year issue.