both that taken in the waters of the State and that brought into the State in a fresh condition, was found by the Court to be purely a food conservation measure, and hence valid.[975] The application of the act to fish brought from outside was held to be justified "by rendering evasion of it less easy."[976] Concurrent Federal and State Legislation THE GENERAL ISSUE Since the turn of the century federal legislation under the commerce clause has penetrated more and more deeply into areas once occupied exclusively by the police power of the States. The result has been that State laws have come under increasingly frequent attack as being incompatible with acts of Congress operating in the same general field. The Court's decisions resolving such alleged conflicts fall into three groups: _first_, those which follow Webster's theory, advanced in Gibbons _v._ Ogden, that when Congress acts upon a particular phase of interstate commerce, it designs to appropriate the entire field with the result that no room is left for supplementary State action; _second_, those in which, in the absence of conflict between specific provisions of the State and Congressional measures involved, the opposite result is reached; _third_, those in which the State legislation involved is found to conflict with certain acts of Congress, and in which the principle of national supremacy is invoked by the Court. Most of the earlier cases stemming from State legislation affecting interstate railway transportation fall in the first class; while illustrations of the second category usually comprise legislation intended to promote the public health and fair dealing. More recent cases are more difficult to classify, especially as between the first and third categories. THE HEPBURN ACT