WASHINGTON — The Supreme Court this morning upheld the nationwide tax subsidies under President Barack Obama’s health care overhaul, in a ruling that preserves health insurance for millions of Americans.

The justices said in a 6-3 ruling that the subsidies that 8.7 million people currently receive to make insurance affordable do not depend on where they live, under the 2010 health care law.

Chief Justice John Roberts again voted with his liberal colleagues in support of the law. Roberts also was the key vote to uphold the law in 2012. Justice Anthony Kennedy, a dissenter in 2012, was part of the majority.

“Congress passed the Affordable Care Act to improve health insurance markets, not to destroy them,” Roberts wrote in the majority opinion.

In a dissent he summarized from the bench, Justice Antonin Scalia said, “We should start calling this law SCOTUScare.” Using the acronym for the Supreme Court, Scalia said his colleagues have twice stepped in to save the law from what Scalia considered worthy challenges.

Justices Samuel Alito and Clarence Thomas joined the dissent, as they did in 2012.

Nationally, 10.2 million people have signed up for health insurance under the Obama health overhaul. That includes the 8.7 million people who are receiving an average subsidy of $272 a month to help pay their insurance premiums.

Of those receiving subsidies, 6.4 million people were at risk of losing that aid because they live in states that did not set up their own health insurance exchanges.