Of Presumptions and Principles

Having quickly read the D.C. Circuit's ObamaCare decision that came down this morning upholding the statute's individual mandate, I'm struck by this line from Judge Laurence Silberman's majority opinion:

No Supreme Court case has ever held or implied that Congress's Commerce Clause authority is limited to individuals who are presently engaging in an activity involving, or substantially affecting, interstate commerce.

I should think that in a free society, living under a Constitution of enumerated and thus limited powers, that the point should be stated precisely the other way around, namely:

No Supreme Court case has ever held or implied that Congress's Commerce Clause authority reaches individuals who are not presently engaging in an activity involving, or substantially affecting, interstate commerce.

In other words, is America's fundamental political principle "everything that is not given (to the government) is retained," or is it rather "everything that is not retained is given"? What is the presumption, and who has the burden of proof? Since the New Deal Court's "constitutional revolution," of course, we've lived, unfortunately, under the latter, and paid the price.