In a brief filed Thursday night, the DOJ said it would not defend the ACA in a lawsuit brought by Texas and other Republican states.

Millions of Texans with pre-existing medical conditions cannot be denied coverage by insurance companies under protections established in the Affordable Care Act. Now, Attorney General Ken Paxton wants to throw patients with pre-existing conditions back to the mercy of insurance companies, and the Trump administration wants to help.

In a brief filed Thursday night, Trump’s Department of Justice (DOJ) sided with 20 GOP attorneys general, led by Paxton, to say that pre-existing conditions protections under the ACA are unconstitutional. The argument in the lawsuit, originally filed by Texas and 19 other states in February, is that eliminating the individual mandate penalty in Congress’ tax bill last year rendered the mandate, and therefore the rest of the health care law, unconstitutional.

In an unusual flouting of precedent, the administration has decided not to defend federal law, instead going after one of the ACA’s most popular provisions, in an election year, no less. The rules at issue prohibit insurance companies from refusing coverage or charging more to certain individuals based on their health or gender. Prior to these protections, people could be routinely denied insurance coverage because they had past medical conditions, or charged more on the basis of being a woman who could become pregnant and need maternity care.

The lawsuit creates further uncertainty in an insurance market already rocked by Trump’s blatant attempts to sabotage the law.

More than 4.5 million adults under 65 in Texas have pre-existing conditions that would make them uninsurable without the ACA protections, according to a 2016 Kaiser Family Foundation analysis. Many more have other health conditions that could lead to much higher costs.

In its new brief, the federal government agreed with Texas and the other states that the individual mandate is unconstitutional, along with pre-existing conditions protections. But while Paxton’s lawsuit goes after the full ACA, the DOJ’s brief says that other measures of the law, such as the insurance exchanges, subsidies and Medicaid expansion, could stand.

Asked to respond to the DOJ’s brief, Paxton’s communications director, Marc Rylander, wrote in an emailed statement, “We’re pleased that the Trump administration agrees with our argument that Obamacare’s individual mandate is unconstitutional and that key parts of Obamacare must be invalidated.” Paxton’s office declined to comment on pre-existing conditions protections specifically.

The ongoing lawsuit has no immediate impact on coverage, and its chances for success may be slim. But it creates further uncertainty in an insurance market already rocked by Trump’s blatant attempts to sabotage the law. And legal experts say it’s an extremely dangerous precedent for the federal government to pick and choose which laws it wants to defend and enforce. (Here’s a helpful Twitter thread from University of Michigan law professor Nicholas Bagley.)

Notably, the lawsuit and brief are also striking indicators of the government’s priorities. Texas already declined a Medicaid expansion that would have covered more than 1 million patients. Now, in the state with the highest uninsured rate in the country, the top law enforcement official is still taking aim at the ACA’s insurance protections — and the president is taking his side in court.