An intellectual mastermind behind perhaps the biggest threat to Obamacare said Friday the Supreme Court made the right call by taking that court case now, rather than waiting what could have been several more years. "The Supreme Court made the right decision," said Michael Cannon, a health policy analyst with the libertarian Cato Institute, about the case that will decide the fate of billions of dollars in financial help given to millions of people. "This issue has to be resolved as quickly as possible if only to resolve the uncertainly surrounding the states, insurers, employers and consumers." Read MoreSupreme Court is 'our only monarchy': IAC's Diller

"But more importantly, this case needs to be resolved quickly to put an end to the greatest scandal of the Obama administration," Cannon said. "This is about whether the Obama administration was subverting democracy." Cannon was waiting to board a plane in Dallas when he got a call from CNBC notifying him that the high court had agreed to hear the appeal of the case, known as King versus Burwell. He and law professor Jonathan Adler have been the leading advocates of the theory that the specific language of the Affordable Care Act does not authorize the federal government to give financial aid to people who buy health insurance through HealthCare.gov.

HealthCare.gov

A federal appeals court in the King case ruled last summer that federal subsidies or tax credits given to nearly 5 million enrollees HealthCare.gov, the federal health-care exchange, were legal.

Plaintiffs in that case argued the subsidies are illegal because the Affordable Care Act only explicitly mentions those often-generous subsidies being issued to customers of state-run exchanges. But the Obama administration says the subsidies are legal and proper because of the ACA's intent to help the uninsured afford health coverage. At the time the Supreme Court said it would hear the case, another virtually identical case was awaiting a re-hearing in the federal circuit appeals court that serves Washington, D.C. There was speculation the Supreme Court would not take up the issue of subsidies unless there ended up being a split between four federal circuits where such cases are winding their way through the system. The Supreme Court's move comes eight days before open enrollment under the ACA begins Nov. 15. A decision in the case could come by next June—after people have already re-enrolled or enrolled in coverage with subsidies that make their plans affordable. For now, the subsidies remain in effect. Both ACA supporters and opponents agree the issue is massive. Read MoreObamacare: Lower prices are possible

If the subsidies are illegal, it would make insurance unaffordable to many Obamacare customers in 36 states. If too many of them dropped their coverage, it could make continuing the plans financially unfeasible for insurers, because they would be likely to have a disproportionate number of unhealthy enrollees left. The elimination of the subsidies also would destroy, in those same states, the looming Obamacare mandate that mid- and large-sized employers start offering health insurance to workers in 2015 or face a fine. And it would cripple in those states the "individual mandate," which requires most Americans to have insurance or pay a fine. Both mandates hinge on the availability of subsidies. Cannon said that while there's speculation the minimum four votes needed to take the case came from the four conservative Supreme Court justices who voted against upholding the ACA in 2012, he "would not be that surprised if some of the Democratic appointees sided with the plaintiffs." "This case is just that clear cut," he said. Cannon has long argued the language in the ACA is so clear that there is no question that financial assistance can only be given to enrollees on the 15 exchanges run by individual states and the District of Columbia. Because of that language, the Obama administration relied on regulations issued by the Internal Revenue Service to formally state that subsidies could also go to customers of HealthCare.gov.

Michael F. Cannon Source: The CATO Institute