A White House statement said: "We expect this ruling will be appealed to the Supreme Court. Pending the appeal process, the law remains in place."

• "The ruling was over a lawsuit filed this year by a group of Republican governors and state attorneys general," per the N.Y. Times.
• U.S. District Court Judge Reed O’Connor in Fort Worth, a George W. Bush appointee, wrote that the individual mandate requiring people to have health insurance "can no longer be sustained as an exercise of Congress’s tax power."

The big picture: This was an amazingly broad ruling. The judge didn't just strike down everything that's related to the individual mandate. He struck down everything, period.

• That includes the parts that everyone likes, like the expansion of Medicaid, young adults staying on their parents' plans — and, of course, coverage of pre-existing conditions.
• Nothing happens right away. The ruling will be appealed, there's no injunction to shut down the law right now, and the Trump administration is making it clear the law stays in place for now.

Why it matters: You should take this ruling seriously. It's getting a lot of criticism from legal experts, including ACA critics, and it could be overturned — but it won't definitely be overturned. This really could end with the ACA being wiped out.

• The ACA has already survived two near-death experiences with the Supreme Court — over the mandate in 2012 and subsidies in 2015.
• But that was before the Kavanaugh Court. If this ruling gets that far, the justices could say the ruling went too far and overturn it.
• But there’s no guarantee that a more conservative court won’t just let the law die.

Political fallout: This could be a nightmare for Republicans in suburbs and swing states.

• The midterms proved that the ACA has gotten more popular since the GOP started trying to repeal it — especially the protections for pre-existing conditions.
• If the law goes away, that goes with it. This is not the fight Republicans want to have. 

The backstory:

• The ruling was issued in a lawsuit by a coalition of Republican-led states led by Texas.
• O'Connor had already signaled in a September hearing that he was open to the red states' arguments.
• The ruling comes one day before the last day of open enrollment for ACA coverage for 2019.
• In an interview with "Axios on HBO," President Trump said he'd reinstate protections for pre-existing conditions if the lawsuit gutted the ACA. But as Axios' Sam Baker notes, Republicans have never come up with a replacement plan that would offer the same level of protection as the ACA.
• Timothy Jost, a legal expert and supporter of the ACA, told Axios' Caitlin Owens that the ruling shouldn't have any effect until Jan. 1, since the tax penalty is still in effect until then. Beyond that, he says, it depends on how the Trump administration reacts and whether a higher court stays the ruling.

Read the ruling:

Go deeper:

There's a new lawsuit over the ACA's individual mandate

Texas lawsuit throws the ACA's future into uncertainty

Exclusive poll: Public fears lawsuit over pre-existing conditions

This story has been updated with more details and reactions from President Trump and Nancy Pelosi.

The law firm suggests 2 main avenues for lawsuits:

• The Eighth Amendment: Denying adequate medical treatment could be considered a form of cruel and unusual punishment.
• Federal civil rights laws: Denying treatment could be considered a form of discrimination against people with disabilities (especially under the Americans with Disabilities Act).

Between the lines: It’s not a shocker that a law firm is suggesting lawsuits — and it acknowledges there hasn’t been a legal precedent yet that establishes a right to treatment for inmates.

• But don’t be surprised if this becomes a new legal movement, as the public health community looks for new ways to reduce deaths from opioid overdoses.