President Obama praised the Supreme Court's health care ruling today, saying that "it's time for us to move forward to implement and where necessary improve" the landmark law that will transform American society.

"Whatever the politics, today's decision was a victory for people all over this country whose lives will be more secure because of this law and the Supreme Court's decision to uphold it," Obama said during brief remarks at the White House.

Obama stressed the provisions of the law that he said will provide health insurance for nearly all Americans when it is fully in place in 2014; he said millions of Americans will not have to give up their existing insurance plans.

The president spoke shortly after the Supreme Court upheld the health care law in a complex opinion that appears to give him a major election-year victory. The decision can be found on the Supreme Court website.

Basically, a majority of the justices said that the individual mandate -- the requirement that most Americans buy health insurance or pay a fine -- is constitutional 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," Chief Justice John Roberts wrote in an opinion that reflected a 5-4 vote on the question.

Roberts -- a conservative appointed by President George W. Bush -- provided the key vote to preserve the landmark health care law, which figures to be a major issue in Obama's re-election bid against Republican opponent Mitt Romney.

Obama said he respects critics of law, and that he will work with others to improve the plan when appropriate. The president added, "it should be pretty clear by now that I didn't do this because it was good politics -- I did it because I believed it was good for the country."

While disdaining the Washington politics surrounding the Supreme Court decision, Obama did note that the law's key provision -- the requirement that most Americans buy some sort of health insurance -- was once backed by some Republicans, including Romney.

For their part, Romney and other Republicans said the decision underscores the need to repeal the law they say is too costly, places too many burdens on job creators, and injects too much government into personal health care decisions.

"Obamacare was bad policy yesterday," Romney said. "It's bad policy today."

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The government had argued that Congress had the authority to pass the individual mandate as part of its power to regulate interstate commerce; the court disagreed with that logic, but preserved the mandate because the fine amounts to a tax that is within Congress' constitutional taxing powers.

The justices decided the tax question on a 5-4 vote, with four Republican appointees in dissent: Anthony Kennedy, Antonin Scalia, Clarence Thomas and Samuel Alito.

Roberts joined four Democratic appointees in upholding the mandate: Ruth Bader Ginsburg, Stephen Breyer, Sonia Sotomayor and Elena Kagan. Obama appointed Justices Sotomayor and Kagan.

In dissent, Kennedy called the major opinion "a vast judicial overreaching."

Ginsburg, meanwhile, wrote that "in the end, the Affordable Care Act survives largely unscathed."

Obama defended the mandate in his remarks, saying in part that "when uninsured people who can afford coverage get sick and show up at the emergency room for care, the rest of us end up paying for their care in the form of higher premiums."

The mandate also discourages people from waiting "until they are sick to buy the care they need. which would also drive up everybody else's premiums."

The announcement will have a major impact on the nation's health care system, the actions of both federal and state governments, and the course of the November presidential and congressional elections.

As lawyers examined the details of the various opinions, political analysts quickly predicted at least a short-term political boost for Obama.

Peter A. Brown, assistant director of the Quinnipiac University Polling Institute, said "you can hear the sigh of relief at the White House" over a big plus for Obama.

"It allows the president's signature achievement to stand," Brown said. "Since politics is the ultimate zero-sum game, what's good for Obama is bad for Gov. Mitt Romney."

Brown also noted that the ruling allows Romney "to continue campaigning against the law and promising to repeal it."

Congressional Republicans, meanwhile, vowed to step up efforts to repeal what they call "Obamacare," should they win control of Congress in the November elections.

"The president's health care law is hurting our economy by driving up health costs and making it harder for small businesses to hire," said House Speaker John Boehner, R-Ohio. "Today's ruling underscores the urgency of repealing this harmful law in its entirety."

House Majority Leader Eric Cantor, R-Va., announced that the GOP-run House will vote July 11 on full repeal of the Obama health care law -- more of a symbolic gesture because the Democratic-run Senate will not follow suit.

Steven Law, president of the Republican super PAC known as American Crossroads, said that "this decision will drive Republican voter intensity sky-high."

The law's individual mandate had been the key question for the court.

Critics called the requirement an unconstitutional overreach by Congress and the Obama administration; supporters say it is necessary to finance the health care plan.

While the individual mandate remains 18 months away from implementation, many other provisions of the health care law already have gone into effect, such as free wellness exams for seniors and allowing children up to age 26 to remain on their parents' health insurance policies.

In his comments at the White House, Obama outlined other provisions:

Insurance companies can no longer impose lifetime limits on the amount of care you receive. They can no longer discriminate against children with pre-existing conditions. They can no longer drop your coverage if you get sick. They can no longer jack up your premiums without reason. They are required to provide free preventive care like checkups and mammograms, a provision that's already helped 54 million Americans with private insurance. And by this August, nearly 13 million of you will receive a rebate from your insurance company because it spent too much on things like administrative costs and CEO bonuses and not enough on your health care.

Not since the Supreme Court confirmed George W. Bush's election in December 2000 -- before 9/11, Afghanistan and Iraq, Wall Street's dive and Obama's rise -- has one case carried such sweeping implications for nearly every American.

Passed by Democrats along strictly partisan lines and still 18 months short of full implementation, the law is designed to extend health coverage to some 32 million uninsured people, ban insurers from discriminating against those with expensive ailments, and require nearly all Americans to buy insurance or pay penalties.

Its passage on March 23, 2010, marked the culmination of an effort by Democrats to overhaul the nation's health care system that dates back to Harry Truman's presidency. The most recent effort by President Bill Clinton in 1994 fell victim to Republican opposition. Since then, lesser changes have been enacted, including creation of a separate Children's Health Insurance Program in the states.