The US Supreme Court on Thursday upheld a bitterly-contested portion of President Barack Obama's landmark healthcare reform, preserving health insurance for millions of Americans.
A triumphant Obama wasted no time in hailing the ruling, which saved his signature domestic policy achievement and could have repercussions for generations to come, calling it a win for "hard-working Americans all across this country."
"This law is working and it's going to keep doing just that," said Obama.
But his Republican foes vowed not to give up the fight over the highly controversial Affordable Care Act, better known as "Obamacare."
By a margin of six to three, the Supreme Court judges ruled in favour of allowing the federal government to subsidise health insurance by giving tax credits to consumers nationwide.
Opponents had argued that it was unconstitutional for the federal government to subsidise insurance in those states that had refused to set up their own insurance exchanges.
"Five years in, this is no longer about a law. This is not about the Affordable Care Act as legislation or 'Obamacare' as a political football. This is health care in America," the president said in the White House Rose Garden.
It was the second big win for Obama in as many days -- after Congress on Wednesday handed him authority to rapidly conclude an ambitious Pacific trade accord, seen as a key pillar of his second-term agenda.
The Affordable Care Act was passed in 2010 and came into force in January 2014.
Since then, 16 million Americans without health insurance have been able to obtain it through their home state or the federal Department of Health and Human Services, which set up the healthcare.gov website.
But out of the 50 US states, 34 -- most of which are Republican governed -- refused to create state health insurance "exchanges," or online marketplaces, requiring their residents to sign up for Obamacare on the federal government's website.
The narrow question before the court was whether some seven million people who signed up for 'Obamacare' via the website were actually entitled to tax subsidies that make the coverage affordable.
But the high court ruled that the law should stand, with two usually conservative justices joining the four generally liberal members of the panel to overturn the challenge.
In a ruling read out by Chief Justice John Roberts, the bench argued that it was clear that the original law had been intended to permit federal subsidies in all states.
Failure to do so would have condemned the law to a "death spiral" by destabilizing the insurance market in states with federally run exchanges, Justice Sonia Sotomayor had said in March when the case was heard.
"It thus stands to reason that Congress meant for those provisions to apply in every state as well... tax credits are available to individuals in states that have a federal exchange," the ruling said.
Republicans mounted several legislative attacks on the law in parallel to the legal assaults and this is the second time in three years that the court has saved it.
The remaining three conservative judges opposed the ruling in a minority opinion presented by Justice Antonin Scalia that argued his colleagues had twisted the language of the bill in order to save it.
"Today's opinion changes the usual rules of statutory interpretation for the sake of the Affordable Care Act," Scalia wrote.
"We should start calling this law SCOTUScare," he added, using the acronym for the Supreme Court.
'Victory for common sense'
Obama's fellow Democrats hailed the announcement."This is a victory for common sense and for all American families," declared Nancy Pelosi, leader of the Democratic minority in the House of Representatives.
"It is long past time for Republicans to abandon their assault on the newfound health security that the Affordable Care Act is providing millions and millions of Americans across the country."
In contrast, Republicans reacted angrily."Republicans will continue to fight tooth and nail to repeal this oppressive law," declared Senator John Cornyn, the party's number two leader in the senate.
"Today's decision doesn't change the fact that Obamacare has been a disaster for the millions of hardworking American families who have seen their health care costs skyrocket or lost their insurance entirely."
Republican contenders in the 2016 presidential race to succeed Obama also slammed the ruling, with Jeb Bush calling it a "fatally flawed law."
But Democratic presidential frontrunner Hillary Clinton tweeted: "Yes! SCOTUS affirms what we know is true in our hearts & under the law: Health insurance should be affordable & available to all."
Health stocks in the US soared after the Supreme Court verdict.
Hospital stocks like HCA Holdings (+8.8%) and Tenet Healthcare (+12.2%) benefited from the Supreme Court ruling that the federal government has authority to subsidise health insurance by giving tax credits to consumers nationwide.