dilemma. Hamilton posited four categories: congressional legislation on (a) subjects committed expressly and exclusively to Congress, (b) subjects over which state authority is expressly negated, (c) subjects over which concurrent authority would be impossible (as “contradictory and repugnant”), and (d) subjects over which concurrent authority is not only possible, but its exercise by both is limited only by considerations of policy (as when one taxing authority is politically deterred from adding too much to the exaction the other authority is already making). But what of those situations involving concurrent powers, like the power over interstate commerce, see, e. g., Cooley v. Board of Wardens of Port of Philadelphia ex rel. Soc. for Relief of Distressed Pilots, 12 How. 299 (1852) (<HOLDING>), when a congressional statute not only binds
holding that commerce clause authorizes congress to punish any particular criminal action even without proof of a relation to interstate commerce when the activity is part of a class of activities determined by congress to affect interstate commerce holding that stock exchanges asserting their rights to engage in interstate commerce free of discriminatory taxes are within the zone of interests protected by the commerce clause recognizing scarborough holding that commerce nexus satisfied upon showing that possessed firearm had traveled at some time in interstate commerce recognizing that  the interstate nexus requirement is satisfied by proof of a probable or potential impact on interstate commerce recognizing power of states to engage in some regulation of interstate commerce