A key portion of ObamaCare has been upheld by the US Supreme Court in a 6-3 decision.

The Supreme Court (SCOTUS) ruled President Barack Obama’s Affordable Care act as a whole made subsidies available for people in all 50 states, not just those who bought insurance through a state exchange.

The high court case was the second major challenge to the healthcare law since its passage.

The decision is major victory for the Obama administration.

“Congress passed the Affordable Care act to improve health insurance markets, not to destroy them,” Chief Justice John Roberts wrote in the opinion.

If the law was overturned, 6.4 million Americans would have been at risk of losing aid.

The 2010 ObamaCare set up a federally run insurance exchange where Americans who were not covered by employers or other governmental could buy health insurance.

Opponents argue that a phrase included in the law, “established by the state,” demonstrated that the healthcare subsidies should have only been available for people in states that set up exchanges.

However, most Americans receiving subsidies purchase healthcare through the federal exchange after many states decided not to set up their own marketplaces.

The Obama administration argued that was a too-narrow reading of the law, which spans near 1,000 pages, and the rest of the legislation makes clear subsidies are intended for those who meet income requirements, regardless of which exchange insurance was purchased from.

Justice John Roberts voted with liberal colleagues in support of the law. He was also the key vote to uphold it in a 2012 case. Justice Anthony Kennedy dissented in 2012, but sided with the majority on June 25.

Justice Anthony Scalia’s wrote in his dissent that the Supreme Court is setting a precedent of favoring some laws over others.

“We should start calling this law SCOTUScare” Justice Anthony Scalia’s wrote.

“Today’s interpretation is not merely unnatural; it is unheard of.”

The upholding of the Affordable Care Act cements President Barack Obama’s biggest legislative victory.

Outside the Supreme Court on June 25, people were celebratory and joyful, chanting “ACA is here to stay!” and “If you’re covered and you know it clap your hands.”