Montana’s attorney general has joined his Ohio counterpart in opposing a Texas judge’s ruling to strike down the Affordable Care Act, as the Republicans go against the Trump administration’s position that the Obama-era health care law is unconstitutional.

Montana Attorney General Tim Fox signed onto Monday’s court filing by Ohio Attorney General Dave Yost, who told The Associated Press last week of his plans to oppose U.S. District Judge Reed O’Connor’s December ruling. The case is now before the 5th U.S. Circuit Court of Appeals, and President Donald Trump’s administration said last week it agrees with the ruling that would kill “Obamacare” if it is upheld.

The brief filed by the Republican attorneys general says O’Connor’s ruling would deprive millions of people in Ohio and Montana of coverage for preexisting conditions and “negatively affect countless others.”

Yost previously told the AP that O’Connor “got it wrong” when he struck down the entire law after Congress eliminated the mandate requiring people without health insurance to pay fines. Yost said the legal doctrine of severability means that even though one section of legislation is repealed, it doesn’t invalidate the entire law.

Fox, who is running for governor in 2020, told Lee Newspapers of Montana that he considers the federal health care law “a train wreck and a nightmare,” but its protection of more than 150,000 state residents with preexisting conditions must be kept.