The Justice Department now believes the entire Affordable Care Act is unconstitutional, a reversal from its position this past summer when the government said changes to the individual mandate were unconstitutional but severable from the whole law.

A Justice Department filing Monday night said the government believes a district court judge's ruling that the entire Obama-era health care law is unconstitutional should be affirmed. Main Justice has a long tradition of defending the constitutionality of federal laws, and, while there are exceptions, it's rare for the department to refuse to defend federal statutes.

U.S. District Judge Reed O'Connor of the Northern District of Texas ruled in December that a congressional tax law passed in 2017—which zeroed out the penalty imposed by the ACA's individual mandate—rendered the entire health care law unconstitutional.

The law, however, remains in effect while the ruling is being appealed to the U.S. Court of Appeals for the Fifth Circuit.

The Justice Department's change in course comes nearly two months after now-Attorney General Bill Barr told senators during his confirmation that he was open to reconsidering the government's stance in the case.

A coalition of states, led by California Attorney General Xavier Becerra, have defended the law after the Justice Department made the controversial decision to drop its defense. The U.S. House of Representatives also stepped in to defend the law and hired former U.S. Solicitor General Don Verrilli, who defended the ACA at the U.S. Supreme Court nearly six years ago.

Texas Attorney General Ken Paxton and several other states are leading that challenge.

Jonathan Adler, a professor at Case Western Reserve University School of Law, called the Justice Department's change in position “alarming.”

“The underlying legal argument is really bad. So the Justice Department is embracing a weak legal argument,” Adler said. “Sometimes the government has obligations, or is in a position to defend something where the legal arguments are not strong, but it still has to defend the government. And here [DOJ] is neither defending the government nor embracing a strong legal argument. And that's kind of noticeable.”

Read the Justice Department's letter below:

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