Individual mandate unconstitutional?

So says the appeals court.

Court strikes down Obamacare's individual mandate as unconstitutional

And what is the opposed argument in defense of its constitutionality?

Well, back when the flap started, it was this.

Defending the constitutionality of the mandate, the government’s primary argument was that Congress can require everyone to buy health insurance using its power under the Commerce Clause of the Constitution, because the failure to buy insurance shifts the costs of health care for the uninsured to health care providers, insurance companies, and everyone who does have health insurance.

. . . .

Justice Ginsburg (joined by Justices Breyer, Sotomayor, and Kagan) agreed with the Chief Justice’s bottom line – that the mandate is constitutional under Congress’s ability to tax – even while disagreeing with his Commerce Clause conclusion; those four Justices would have held that Congress could use its power to regulate commerce to pass the mandate.