WASHINGTON (Reuters) - The Democratic-controlled U.S. House of Representatives and 20 Democratic-led states asked the Supreme Court on Friday to declare that the landmark Obamacare healthcare law does not violate the U.S. Constitution as lower courts have found in a lawsuit brought by Republican-led states.

FILE PHOTO: The U.S. Supreme Court in Washington, D.C., U.S., June 17, 2019. REUTERS/Leah Millis

The House and the states, including New York and California, want the Supreme Court to hear their appeals of a Dec. 18 ruling by the New Orleans-based 5th U.S. Circuit Court of Appeals that deemed the 2010 law’s “individual mandate” that required people to obtain health insurance unconstitutional.

The petitions asked the Supreme Court, which has a 5-4 conservative majority, to hear the case quickly and issue a definitive ruling on the law, formally called the Affordable Care Act, by the end of June.

Texas and 17 other conservative states - backed by President Donald Trump’s administration - filed a lawsuit challenging the law, which was signed by Democratic former President Barack Obama in 2010 over strenuous Republican opposition. A district court judge in Texas in 2018 found the entire law unconstitutional.

“The Affordable Care Act has been the law of the land for a decade now and despite efforts by President Trump, his administration and congressional Republicans to take us backwards, we will not strip health coverage away from millions of Americans,” New York Attorney General Letitia James said.

Obamacare, considered Obama’s signature domestic policy achievement, has helped roughly 20 million Americans obtain medical insurance either through government programs or through policies from private insurers made available in Obamacare marketplaces. Republican opponents have called it an unwarranted government intervention in health insurance markets.

Congressional Republicans tried and failed numerous times to repeal Obamacare. Trump’s administration has taken several actions to undermine it.

In 2012, the Supreme Court narrowly upheld most Obamacare provisions including the individual mandate, which required people to obtain insurance or pay a financial penalty. The court defined this penalty as a tax and thus found the law permissible under the Constitution’s provision empowering Congress to levy taxes.

In 2017, Trump signed into law tax legislation passed by a Republican-led Congress that eliminated the individual mandate’s financial penalty. That law means the individual mandate can no longer be interpreted as a tax provision and therefore violates the Constitution, the 5th Circuit concluded.

In striking down the individual mandate, the 5th Circuit avoided answering the key question of whether the rest of the law can remain in place or must be struck down, instead sending the case back to a district court judge for further analysis.

That means the fate of Obamacare remains in limbo. The fact that the litigation is still ongoing may make the Supreme Court, which already has a series of major cases to decide in the coming months, less likely to intervene at this stage.