A sharply divided U.S. Supreme Court on Thursday upheld the centerpiece of President Barack Obama's signature healthcare overhaul law that requires that most Americans get insurance by 2014 or pay a financial penalty.
"The Affordable Care Act's requirement that certain individuals pay a financial penalty for not obtaining health insurance may reasonably be characterized as a tax," Chief Justice John Roberts wrote for the court's majority in the opinion.
"Because the Constitution permits such a tax, it is not our role to forbid it, or to pass upon its wisdom or fairness," he concluded. The vote was 5-4.
In another part of the decision and in a blow to the White House, a different majority on the court struck down the provision of the law that requires the states to dramatically expand the Medicaid health insurance program for the poor.
The upholding of the insurance purchase requirement, known as the "individual mandate," was a major election-year victory for Obama, a historic ruling on the law that aimed to extend coverage to more than 30 million uninsured Americans.
The 2010 law constituted the $2.6 trillion U.S. healthcare system's biggest overhaul in nearly 50 years.
Critics of the law had said it meddles too much in the lives of individuals and in the business of the states.
Twenty-six of the 50 U.S. states and a small business trade group challenged the law in court. The Supreme Court in March heard three days of historic arguments over the law's fate.
The court's ruling on the law could figure prominently in the run-up to the Nov. 6 election in which Obama seeks a second four-year term against Republican challenger Mitt Romney, who opposed the law.