President Barack Obama said his landmark health care law is "here to stay" after it survived its second major legal challenge Thursday.

"This law is working. And it's going to keep doing just that," Obama said in a press conference.

The Supreme Court ruled in a 6-3 decision Thursday that federal subsidies—which help nearly 6.4 million people pay for their Obamacare health plans—are legal under the Affordable Care Act. A pillar of Obama's first campaign and tenure in office, the law was designed to reduce the number of uninsured Americans.

Read MoreSupreme Court approves Obamacare subsidies on HealthCare.gov



"This not an abstract thing anymore. This is not a set of talking points. This is reality. We can see how the law is working. It works exactly as it is supposed to," he said.

The latest decision exacerbated the political tension surrounding the health law. Reactions immediately came from both Obama's Democratic and the opposition Republican Party, with officials looking ahead to how the 2016 presidential election could affect U.S. health care.

In a press conference, House Speaker John Boehner (R-OH) said the ruling does not change a "fundamentally broken" system. He added that Republicans will continue efforts to repeal the law and "put the American people back in charge of their own health care."

Read MoreHealth care stocks surge on Obamacare ruling

