Supreme Court Upholds Obamacare Subsidies, President Says ACA 'Is Here to Stay' The decision signals another win for the president.

WASHINGTON -- The U.S. Supreme Court sided today with the Obama administration over its major healthcare overhaul, upholding federal subsidies across the country.

In a 6-3 ruling, the nation’s highest court ruled that critics’ reading of Obamacare might make sense in isolation, but not when viewed in a larger context and in light of the intention of the law.

"After multiple challenges to this law before the Supreme Court, the Affordable Care Act is here to stay," President Obama said.

Flanked by Vice President Joe Biden, Obama added that had the Supreme Court struck down the use of subsidies on the federal exchange, “America would have gone backwards. That’s not what we do."

It’s the second time the Supreme Court -- and its conservative chief justice, John Roberts -- has backed controversial portions of Obamacare. The first ruling was in 2012.

Justice Antonin Scalia wrote an angry dissent, saying the Supreme Court’s pair of decisions over Obamacare will “surely be remembered through the years” as evidence the court does “whatever [it] takes to uphold and assist its favorites.”

The chairman of the Senate Homeland Security Committee, Sen. Ron Johnson, R-Wisconsin, called the ruling “incredibly disappointing.”

“Obamacare has never been accepted by the American people,” Johnson said. “The harm that the law inflicts shows that the people were right. Congress must move America past this unaffordable, destructive law.”

The decision has a major impact on the millions of Americans who are receiving financial assistance from the federal government to buy health insurance.

Obamacare -- technically titled The Affordable Care Act -- gave states the option to build their own healthcare marketplaces or simply use one operated by the federal government.

In all, 34 states decided to rely on the federal “exchange.” And more than 6 million low- to moderate-income Americans are now receiving subsidies of on average $260 a month through the federal exchange, according to Health and Human Services Secretary Sylvia Burwell.

But in a lawsuit challenging the law, critics insisted the federal government is not allowed to subsidize insurance in states that rejected their own exchange for the federal system. Those critics based their argument on a single phrase in Obamacare that refers only to participants enrolled “through an Exchange established by the State.”

“If subsidies are authorized for all Exchanges, why does [the law] specify an Exchange ‘established by the State’?” petitioner David King and others wrote in their brief to the Supreme Court.

The White House has maintained, though, that in drafting and passing Obamacare, Congress clearly intended to offer insurance subsidies to those participating in both the federal and state exchanges.

Last week, Burwell said the administration was “in a very strong position in the case,” based on the wording of the law and “the intention of the law.”

She warned an adverse ruling would likely mean millions of Americans would lose subsidies and be unable to afford health insurance coverage.

With only the sickest people in the insurance marketplace then, costs for coverage “drive up,” she added.

In all, at least 10.2 million Americans have signed up for health coverage through Obamacare, according to Burwell’s department.

She indicated an adverse ruling would mean governors in states without exchanges would have to decide whether to create them, and Congress would face a decision over whether to intervene through legislation.

ABC News’ Nancy Gabriner contributed to this report

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