As previous Commerce Clause cases have all involved physical activity, as opposed to mental activity, i.e. decision-making, there is little judicial guidance on whether the latter falls within Congress’s power...However, this Court finds the distinction, which Plaintiffs rely on heavily, to be of little significance. It is pure semantics to argue that an individual who makes a choice to forgo health insurance is not "acting," especially given the serious economic and health-related consequences to every individual of that choice. Making a choice is an affirmative action, whether one decides to do something or not do something. They are two sides of the same coin. To pretend otherwise is to ignore reality.

It doesn't look like he's saying that mental activity can be regulated by Congress, but rather the claim that deliberate choice not to do something is "mental activity" rather than "physical activity," and thus cannot be regulated, is a meaningless semantic game.