The U.S. Supreme Court has upheld the individual mandate in President Obama's controversial healthcare law, in a 5-4 ruling.

The requirement that Americans purchase health insurance cannot be upheld under the Commerce Clause but can stand as a tax, the majority ruled.

"The Affordable Care Act's requirement that certain individuals pay a financial penalty for not obtaining health insurance may reasonably characterized as a tax. Because the Constitution permits such a tax, it is not our role to forbid it, or to pass upon its wisdom or fairness," the justices said in the ruling.

On its face the ruling is a victory for the Obama administration, but GOP political strategist Karl Rove warned the fight over 'Obamacare' is far from over.

"If this is actually the decision, it's a boost for the president, but it doesn't make the controversy go away," Rove told Fox News. "In fact, it probably enhances the controversy."

Chief Justice John Roberts and justices Stephen Breyer, Ruth Bader Ginsburg, Elena Kagan and Sonia Sotomayor represented the majority opinion.

Justices Samuel Alito, Anthony Kennedy, Antonin Scalia and Clarence Thomas dissented.

"The act before us here exceeds federal power both in mandating the purchase of health insurance and in denying non-consenting states all Medicaid funding," the dissenting justices said in a joint statement.

Meanwhile, GOP lawmakers are calling for the law's repeal.

"Today's decision makes one thing clear: Congress must act to repeal this misguided law. Obamacare has not only limited choices and increased health care costs for American families, it has made it harder for American businesses to hire," Senate Republican Leader Mitch McConnell said in a statement.

"Today's decision does nothing to diminish the fact that Obamacare's mandates, tax hikes, and Medicare cuts should be repealed and replaced with common sense reforms that lower costs and that the American people actually want," the Kentucky lawmaker continued.

"It is my hope that with new leadership in the White House and Senate, we can enact these step-by-step solutions and prevent further damage from this terrible law," he said.