The judge sided with 20 Republican state attorneys general and governors, as well as two individuals, who argued that when Congress eliminated the individual mandate penalty - by reducing it to $0 - it rendered the mandate itself unconstitutional and that the rest of the law therefore can not stand.
Trump tweeted again on Monday, saying, "We have a chance, working with the Democrats, to deliver great HealthCare!" "Today's misguided ruling will not deter us: our coalition will continue to fight in court for the health and well-being of all Americans", said California Attorney General Xavier Becerra, who is leading a coalition of states defending the ACA.
Some conservative critics have accused him of providing the roadmap to save ObamaCare, citing a 2011 case where Kavanaugh dissented against the ruling but acknowledged the Affordable Care Act's "individual mandate provision" could fit "comfortably within Congress' Taxing Clause power".
Dr. Ezekial Emanuel, who also developed Obamacare, is calling the ruling "silly" and is confident it will be upheld for a second time at the Supreme Court.
The Affordable Care Act returned to the front page this weekend when a federal district court in Texas issued an opinion striking down the entire law as unconstitutional.
Judge O'Connor agreed. He said further that the law and its mandate could not be separated, and with this key part missing, the whole law should collapse, like a pillar of blocks in the game Jenga. The sprawling law includes not only health insurance exchanges and an expansion of Medicaid, but also protections for people with pre-existing conditions, requirements for what insurance must cover and much more. "A good way to show that you're exhausted of people trying to take away your health care is to go get covered".
President Trump is ready to go with the new Congress in January.
Supporters of the law immediately said they would appeal.
As "this decision makes it way through the courts, which will take months, if not years, the law remains in place and will likely stay that way", he added.
"In the interim, it provides Congress with a real opportunity recognizing that Obamacare is on life support to pull together and make a determination of the things that we need to do to provide sufficient healthcare for all Americans including pre-existing conditions", he said, after show host Steve Doocy complained his own daughter has deductibles on her own Obamacare plan that are too hard to meet.
After the judge's ruling, White House press secretary Sarah Sanders said, "We expect this ruling will be appealed to the Supreme Court".
This would put Roberts in a potentially awkward spot. But with that "tax" - or penalty - having been removed starting next year, Republicans challenging the law in this case argued the program is now illegal.
Twenty states, including Texas, filed a case claiming that without the penalty, the mandate can no longer be upheld as a tax.
The healthcare industry has long awaited a decision in Texas v. Azar, since the US District Court for the Northern District of Texas heard arguments this past September. Our guess is that even the right-leaning Fifth Circuit Court of Appeals judges will overturn Judge O'Connor on this point.