Gun-Free School Zones Act is a criminal statute that by its terms has nothing to do with "commerce" or any sort of economic enterprise, however broadly one might define those terms. act is not an essential part of a larger regulation of economic activity, in which the regulatory scheme could be undercut unless the intrastate activity were regulated. It cannot, therefore, be sustained under our cases upholding regulations of activities that arise out of or are connected with a commercial transaction, which viewed in the aggregate, substantially affects interstate commerce.