In a dramatic move, the Trump administration declared its intention to refuse to defend the Affordable Care Act from a federal lawsuit by 20 GOP-controlled states who are arguing that Congress’ repeal of the individual mandate renders parts of the rest of the health care law unconstitutional, according to a filing from the Department of Justice Thursday evening.

In particular, the administration is arguing that the ACA’s ban on discrimination based on pre-existing conditions and limits on charging older patients higher premiums are invalid, and they are requesting that the court put a halt to those provisions in January of 2019, when enforcement of the individual mandate is set to be terminated.

The change was signaled earlier on Thursday when three career DOJ attorneys withdrew from the lawsuit and a political appointee signed on to represent the administration in the case, which is pending before the District Court for the Northern District of Texas.

A DOJ spokesperson declined to comment to TPM about the change in attorneys, characterizing it as “personnel issues.”

The Trump administration and the GOP-controlled House and Senate made several attempts to repeal the ACA in 2017. Following the failure of those legislative salvos — save for the successful repeal of the individual mandate as part of a massive package of tax cuts — the administration set about chipping away at the health care law piece by piece using executive orders and Department of Health and Human Services regulations. Those moves, particularly the anticipated introduction of cheap, skimpy, short-term and limited-benefit health care plans, are expected to drain healthy consumers from the ACA market and drive up premiums for those who remain.

Thursday’s legal brief is a new phase of the administration’s crusade against the ACA. It is extremely rare, but not unprecedented, for the Justice Department to refuse to defend a federal law, as the agency is generally duty-bound to argue in defense of any current laws or policies that come under legal challenge. Most recently, President Obama directed his DOJ not to defend the Defense of Marriage Act, which was later struck down by the Supreme Court.

In this case, even though the DOJ is refusing to defend the ACA, several attorneys general representing blue states, led by California, have intervened in defense of the law and will argue that it should be preserved in its entirety.

The red states seeking to invalidate the ACA argue that the Supreme Court only upheld the constitutionality of the law in 2012 because the individual mandate was considered a tax. Because Congress repealed that tax — the penalty for not purchasing health insurance — as part of the tax reform bill earlier this year, they argue that the requirement to buy health coverage is now unconstitutional. On Thursday, the DOJ agreed with this interpretation.

“The reasoning is worse than ridiculous,” a source involved in the lawsuit on behalf of groups defending the ACA. “And the consequence is that starting next year – sick and old people will have to pay much more for coverage – the key element of the Obama reforms.”

Read the filing below:

In a letter to House Minority Leader Nancy Pelosi, Attorney General Jeff Sessions outlined his reasoning for the move, saying that key piece of the ACA are “inseverable” from the individual mandate and thus must be abolished following its repeal.