A spokesperson from the Centers for Medicare & Medicaid Services told Fox News early Saturday that open enrollment for Affordable Care Act’s health insurance will continue despite the federal judge's ruling that the law is unconstitutional and must be "invalidated in whole.”

U.S. District Judge Reed O'Connor, a federal judge in Texas appointed by President George W. Bush, ruled that last year's tax cut bill knocked the constitutional foundation from under Obamacare by eliminating a penalty for not having coverage. The rest of the law cannot be separated from that provision and is therefore invalid, he wrote.

The decision came on the evening before the Dec. 15 deadline for Americans.

The spokesperson from CMS told Fox that the judge’s decision, which was applauded by President Trump, is still working its way through the courts and is not the final word on the matter.

"There is no impact to current coverage or coverage in a 2019 plan," the spokesperson said.

Congress is unlikely to act while the case remains in the courts. Numerous high-ranking Republican lawmakers have said they did not intend to also strike down popular provisions such as protection for people with pre-existing medical conditions when they repealed the ACA's fines for people who can afford coverage but remain uninsured.

Xavier Becerra, the California attorney general, vowed to appeal the decision in the U.S. Court of Appeals for the Fifth Circuit in New Orleans.

"Today’s ruling is an assault on 133 million Americans with pre-existing conditions, on the 20 million Americans who rely on the A.C.A.’s consumer protections for health care, on America’s faithful progress toward affordable health care for all Americans," Becerra said in a statement, obtained by The New York Times.

Rep. Nancy Pelosi, D-Calif., who is expected to become House speaker in January, vowed to fight what she called an "absurd ruling."

Trump tweeted his support for the ruling, saying, "Obamacare has been struck down as an UNCONSTITUTIONAL disaster!" He continued, "Now Congress must pass a STRONG law that provides GREAT healthcare and protects pre-existing conditions."

About 20 million people have gained health insurance coverage since the ACA passed in 2010 without a single Republican vote. Currently, about 10 million have subsidized private insurance through the health law's insurance markets, while an estimated 12 million low-income people are covered through its Medicaid expansion.

The White House said late Friday that it expects the ruling to be appealed to the Supreme Court. The five justices who upheld the health law in 2012 in the first major case -- Chief Justice John Roberts and the court's four liberals -- are all still serving.

The Associated Press contributed to this report