In fact, the only basis for the mandate’s constitutionality, according to Roberts, is that it’s a tax — not a fine, penalty, or anything else. This is a vital point, because when Republicans passed their tax reform legislation in December 2017, they included a provision in the law that lowers the individual mandate penalty to $0 beginning in January 2019, effectively eliminating any hope the individual mandate could still be considered a “tax.”
If the tax-less individual mandate is now found to be unconstitutional, it could very likely result in the entire healthcare law being struck down. In their 2012 dissenting opinion, four Supreme Court judges argued the ACA could not survive absent the individual mandate. Although Roberts never addressed the question in his opinion, there are good reasons to believe he should agree to throw the entire law out.
When determining whether a law should survive despite having at least one provision determined to be illegal, the Supreme Court has enacted a two-part test. In his 2012 dissent, Scalia explained the first part is “whether the now truncated statute will operate in the manner Congress intended. If not, the remaining provisions must be invalidated.”
Because Congress is the one that determined the Obamacare fine should be $0, it would likely be difficult to argue the ACA is operating in a manner it didn’t intend. But the second part of the test poses a much more difficult problem.
“Second, even if the remaining provisions can operate as Congress designed them to operate, the Court must determine if Congress would have enacted them standing alone and without the unconstitutional portion,” Scalia wrote. “If Congress would not, those provisions, too, must be invalidated.”
The reasoning seems solid, but you never know what the Roberts Court might do.