Insurers, physicians and hospitals are siding with the Affordable Care Act, and Democrats, in a lawsuit brought by GOP state leaders and supported by the Trump administration.

In a brief (PDF) opposing the suit, several physician groups claim the plaintiffs lack legal standing because citizens have a voluntary choice to purchase healthcare and that the law can stand as a "tax" even without generating revenue.

Groups on the amicus brief include the American Medical Association, the American Academy of Family Physicians, the American College of Physicians, the American Academy of Pediatrics, and the American Academy of Child and Adolescent Psychiatry. They argued that Republican attorneys general lacked standing because they could not prove their states had suffered harm or injury from the ACA.

"Invalidating the guaranteed-issue and community rating provisions—or the entire ACA—would have a devastating impact on doctors, patients, and the American healthcare system as a whole," the groups wrote.

Twenty Republican state leaders filed the lawsuit earlier this year, which the Trump administration has recently said it supportsSeventeen Democratic attorney's general joined the suit in April in defense of the 2010 law. 

One of the GOP's main arguments is that because the mandate's penalty was removed last year, the law can no longer be considered a tax.

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“Absent the individual mandate, the ACA is an irrational regulatory regime governing an essential market,” the attorneys general stated in their initial complaint

The provider groups also countered that despite a zeroed out penalty, the minimal essential coverage provision can still be justified as a tax despite not raising revenue, citing a previous Fifth Circuit court ruling. America's Health Insurance Plans made a similar argument in their brief (PDF.)

Additionally, they contend that rolling back pre-existing condition protections would  "have a devastating impact on doctors, patients, and the American health care system" and "leave millions without much-needed insurance."

Four hospital groups, including the American Hospital Association and the Federation of American Hospitals, filed a brief (PDF) of their own, and contend that the individual mandate is severable from the rest of the law, and that the pre-existing condition protections should remain.