Why did Judge Roger Vinson initially declare the entire Affordable Care Act unconstitutional?

In January 2011, U.S. District Court Judge Roger Vinson declared the entire Affordable Care Act unconstitutional based on his interpretation of the commerce clause.

Vinson agreed with the plaintiffs that the commerce clause limits Congress’s regulatory authority to "activities." He concluded that the law’s individual mandate, which required individuals to purchase health insurance, was a regulation of "inactivity" rather than activity, and therefore exceeded congressional power.

Furthermore, Vinson determined that the individual mandate was not severable from the rest of the Patient Protection and Affordable Care Act (PPACA). Because he found the mandate to be unconstitutional and inextricably linked to the other provisions of the law, he ruled that the entire act was invalid.1