The legal dispute begins with 12 words enshrined in Article I, Section 8 of the Constitution: “Congress shall have power … to regulate commerce … among the several states.”
Congress has used this authority to pass a wide range of federal laws involving interstate commerce and economic activities affecting the states. The Supreme Court has rarely challenged efforts to broadly construe congressional authority under the Constitution’s commerce clause.
But problems have arisen whenever the court has tried to identify the boundaries of this federal commerce authority.
The Constitution was written in part to constrain the national government within enumerated powers. For example, the 10th Amendment notes that the “powers not delegated to the [federal government] by the Constitution … are reserved to the states respectively, or to the people.”
That means the national government has no power to act beyond the role assigned it under the Constitution. In contrast, the states retain the broadest powers – including a general police power that would allow a state government unquestionably to order a statewide version of the ACA.
This is the situation in Massachusetts, where most people have been required to buy health insurance since 2007.
The question before the Supreme Court is whether federal power is broad enough to permit Congress to order a nationwide individual mandate.
Important 'commerce clause' cases of yore
To answer that question, the court must look back through history at earlier Supreme Court decisions that have defined the reach of federal power under the commerce clause. Those cases involve wheat, marijuana, guns near schools, and violence against women.