The U.S. Justice Department said in a legal filing Monday that it agrees with a Texas district court's ruling that the Affordable Care Act, also known as "Obamacare," is unconstitutional, throwing the future of the health-care law in doubt. "The Department of Justice has determined that the district court's judgment should be affirmed," the DOJ said in a filing to the 5th Circuit Court of Appeals in New Orleans. The Texas ruling last December said the law's individual mandate was unconstitutional, invalidating the entire ACA. The Justice Department had previously argued to keep the law mostly intact, but that the law's protection of pre-existing conditions needed to be struck down. The filing means the government agrees the entire law should be struck and it will not challenge the ruling in its lengthy appeal process. Health-insurance stocks turned volatile immediately following the original Texas ruling, as it brought uncertainty over future health-insurance costs. Experts said in December that the case may reach the U.S. Supreme Court in 2020.