The increase of criminal activities interstate in scope, and the growing dissatisfaction with state enforcement of local laws, have focused attention of late upon the power of Congress to regulate crime under the commerce clause of the Constitution. Outstanding among proposals for congressional legislation are the following: making interstate felonies federal offenses; punishing criminals who flee across state lines after committing a crime; and restricting the sale and transportation of firearms. Most, if not all, of this suggested legislation must rest on the commerce clause for its validity. We purpose here to discuss the nature and scope of this power, and, without considering the merits of the proposed laws, to inquire whether they can be brought under it.