A coalition of state attorneys general defending the Affordable Care Act has taken the first step in appealing a federal judge's ruling in Texas that declared the entirety of the 2010 law unconstitutional.

The group of states, led by California Attorney General Xavier Becerra, is expected to argue that the law's individual mandate remains constitutional despite a federal tax law passed last year that zeroed out its tax penalty. The AGs contend that even if the individual mandate is struck down, the rest of the law's provisions should be allowed to stand.

The states filed their notice of appeal in the Northern District of Texas on Thursday. The attorneys general in a call with reporters described the underlying ruling by U.S. District Judge Reed O'Connor of the Northern District of Texas as based on a “flimsy theory” and “ludicrous.”

The case will go before the U.S. Court of Appeals for the Fifth Circuit.

Phil Weiser, the state attorney general-elect in Colorado, indicated Thursday that he plans to join the coalition of states defending the Affordable Care Act. Weiser said O'Connor's ruling finding the ACA's individual mandate is inseverable from the whole law goes against the “mainstream view on all sides of the aisle.”

“Congress had the opportunity to, and did not, repeal the law,” Weiser said. “It's not for a judge to then effectively repeal the whole law. All Congress did, and all that this law is based on is it reduced the tax penalty. To take that action and try to leverage it into invalidating the entire law … it's an affront to the rule of law.”

The AGs' filing comes shortly after O'Connor stayed his ruling Dec. 30 after finding residents in many states have already purchased their health insurance plans for 2019.

O'Connor initially ruled Dec. 14 that a congressional tax law passed last year, which zeroed out the penalty imposed by the ACA's individual mandate, rendered the whole health care law unconstitutional.

A group of mostly conservative states, led by Texas Attorney General Ken Paxton, filed their constitutional challenge to the ACA in February. Those states contended that the congressional tax law effectively rendered the individual mandate unconstitutional, as well as two protections they said were inseverable from the mandate: the law's community rating requirement and its guaranteed coverage for pre-existing conditions.

Becerra and the cluster of Democratic state attorneys general have led the fight defending the health care law's survival after the Justice Department dropped its defense in June.

Read more: