tinct reserved power, may pass laws similar or identical in their provisions, and that, therefore, the question whether a given State enactment is a regulation of commerce or not cannot, in doubtful cases, be answered without scrutinizing the purpose for which the Legislature passed it; that this principle was applied in the case of Miln v. New York, and recognized and developed by Woodbury, J., in his opinion in the License and Passenger Cases, he laying down the further principle, that in all the cases of doubt as to the purpose of a State law its constitutionality should be sustained; that, in the course of the controversy over the question of concurrency or exclusiveness of the commercial power of Congress, the principles laid down and the distinctions taken in the earlier cases were, to some extent, lost sight of, and were covered up and obscured by the dust and smoke of that controversy; that, in the case of Cooley v. Board of Wardens, that controversy was settled by what appears at first sight to be a compromise decision, to the effect that the commercial powers of Congress are in part exclusive and in part concurrent, which decision, however, on closer analysis, appears to be a practical victory for the cause of “exclusiveness,” the part of the commercial power which is held concurrent being apparently intended to cover such laws, like quarantine laws, health laws, etc., which affect foreign or interstate commerce, but are passed with a different purpose from that of regulating such commerce, and which, consequently, are not to be deemed regulations of foreign or interstate commerce; that the more recent cases do not attempt to lay down general principles touching the means of distinguishing valid State laws affecting foreign or interstate commerce from State laws invalid as regulations of foreign or interstate commerce; that while the modern decisions amply recognize the principle that an intention to regulate foreign or interstate commerce is the criterion of a regulation of foreign or interstate commerce, to the extent of holding State laws, ostensibly framed for other purposes, unconstitutional, if really passed with the intent of regulating foreign or interstate commerce, there appears to be a tendency to abandon that criterion in the case of laws “unreasonably” burdening or impeding foreign or interstate commerce, though passed without intent to regulate such commerce, and to hold such laws invalid as regulations of foreign or interstate commerce, regardless of their object or purpose. We have seen that this tendency of
