In a brief filed Thursday, the Justice Department sided with Texas and a coalition of other Republican-led states that had filed a suit challenging the constitutionality of Obamacare. While it is uncommon for the Justice Department to go against federal law, Attorney General Jeff Sessions said that he acted with the “approval of the President of the United States.”

Here’s their argument, and what they want.

What does the suit want?

The filing declares unconstitutional the so-called individual mandate—which requires almost all Americans to purchase health insurance or pay a “tax” if they don’t—and calls for several elements of ACA to be invalidated. These include a “ban on insurers denying coverage and charging higher rates to people with pre-existing health conditions.” The Justice Department reportedly also wants to repeal limits on insurance costs based on gender and age.

Nevertheless, the Justice Department’s position did not go quite as far as the Texas suit. In it, the states deem the entirety of Obamacare and its regulations invalid.

What is their argument?

In 2012, the Supreme Court upheld the individual mandate as a legal use of Congress’s taxing power. But under the GOP tax bill signed into law last December, tax penalties for people without insurance were eliminated.

The Justice Department thus claims that the individual mandate is unconstitutional as of Jan. 1. With the repeal of the mandate penalty, the mandate became a simple requirement to buy a service—not a tax—and is therefore not constitutional.

“The individual mandate thus still exists, but it will no longer be fairly possible to describe it as a tax because it will no longer generate any revenue,” the Justice Department said in its brief on Thursday. “As of 2019, therefore, the individual mandate will be unconstitutional under controlling Supreme Court precedent holding that ‘the federal government does not have the power to order people to buy health insurance.’”

Protections for individuals with pre-existing conditions are connected with the individual mandate, according to the Justice Department, meaning that they must also be struck down.

What do other states say?

California and 15 other states filed an opposing brief on Thursday defending the law. A definitive court ruling “could be months away” according to The New York Times, with appeals lasting many more. In the meantime, the existing law will likely remain. However, if the federal court sides with the plaintiffs, those with pre-existing conditions could once again be denied coverage.