Charles Kolb is president of the Committee for Economic Development and was a domestic policy adviser to Bush the Elder. Over at Huffington Post, he articulates why (he thinks) the Constitution's Commerce Clause empowers Congress to force people to purchase health insurance, but not broccoli. That is to say, he offers (what he thinks is) a limiting principle that (he thinks) would enable the Supreme Court to uphold ObamaCare's individual mandate, but still leave some constraints on Congress's ability to force people to buy things. Like broccoli.
Yet Kolb's proposed limiting principle is no more a limiting principle than Harvard law professor Noah Feldman's proposed limiting principle, because the two make the same argument. Almost verbatim. So rather than regurgitate my response to Feldman, I'll just link to it.
Okay, I'll regurgitate this part:
Like every other so-called limiting principle offered by ObamaCare’s defenders, Feldman’s[/Kolb's] has no basis in the Constitution or any other law. It is a post hoc rationalization, made by people who are shocked to find themselves before the Supreme Court, defending the constitutionality of their desire to bully others into submission.