"4. This power over commerce among the states, so conferred upon congress, is com plete in itself, extends incidentally to every instrument and agent by which such com merce is carried on, may be exerted to its utmost extent over every part of such com merce, and is subject to no limitations save such as are prescribed in the constitution. But, of course, it does not extend to any mat ter or thing which does not have a real or substantial relation to some part of such commerce.
"5. Among the instruments and agents to which • the power extends are the railroads over which transportation from one state to another is conducted, the engines and cars by which such transportation is affect ed, and all who are in any wise engaged in such transportation, whether as common carriers or as their employes.
"6. The duties of common carriers in re spect of the safety of their employes, while both are engaged in commerce among the states, and the liability of the former for in juries sustained by the latter, while both are so engaged, have a real or substantial relation to such commerce and therefore are within the range of this power." In the Covington Bridge Case, Covington & C. Bridge Co. v. Kentucky, 154 U. S. 204, 14 Sup. Ct. 1087, 38 L. Ed. 962, the Supreme Court cases with respect to the power of the states over commerce have been divided into three classes, which division is repeated in Southern R. Co. v. Reid, 222 U. S. 424, 32 Sup. Ct. 140, 56 L. Ed. 257: First, those in which the power of the state is exclusive. (Cases in which this pow er may be exercised by the states are enu merated infra under the subtitle "When the State Power is Exclusive.") Second, those in which the states may act in the absence of legislation by congress. In the case cited, it is said that these cases embrace what may be termed "concurrent jurisdiction," but it does not appear that such jurisdiction ever exists, because the power of the states is terminated instantly by legislation of congress on the subject. (See Wm, under subtitle "State Action Valid in Case of Non-Action by Congress.") Third, cases in which the action of con gress is exclusive and the states cannot act at all. (See lafra, under subtitle "When the Power of Congress is Exclusive.") Neither this, nor in fact any other, classi fication of cases is satisfactory, nor is there any one of them which has been uniformly adhered to by the Supreme Court.
It may probably be fairly stated as the result of the decisions on the commerce clause that while the states have exclusive jurisdiction of certain local matters, which are controlled by virtue of its reserved police power, and they have also exclusive control of intrastate commerce, the clause of the constitution under consideration gives to congress absolute control of interstate and foreign commerce, to become at its will ex clusive of all other authority. Upon many
subjects affecting this commerce, the states do legislate and their statutes are held valid, Wit this is solely because congress has not acted, and once it does so, the power of the state ends. State legislation is not forbid den in matters either local in their opera tion, or intended to be mere aids to com merce, for which special regulations can more effectually provide, such as harbors, pilotage, beacons, buoys, and other improve ments of harbors, bays, and rivers within a state, if their free navigation be not there by impaired ; congress by its inaction in such matters virtually declares that till it deems best to act, they may be controlled by the states ; County of Mobile v. Kimball, 102 U. S. 691, 26 L. Ed. 238, per Field, J.
As to certain subjects the power of congress is exclusive, and the states cannot inter fere in any case, and the line of distinction is plainly marked. The cases in which the state may act so long as congress does not, are those which relate to matters of local concern, and which do not require a general uniform regulation applying to the whole country; Rhea v. R. Co., 50 Fed. 16; Card well v. Bridge Co., 113 U. S. 205, 5 Sup. Ct. 423, 28 L. Ed. 959. On the other hand, as to all matters affecting interstate com merce, directly or indirectly, national in char acter and requiring a uniform system or regulation throughout the country, the pow er of congress to regulate them is exclusive. This in brief seems to be the result of the decisions, which will be found cited in this title under the various subdivisions of the subject. The distinction between cases where the state may or may not act in case of non-action by congress, is well expressed in Leisy v. Hardin, 135 U. S. 100, 10 Sup. Ct. 681, 34 L. Ed. 128, to this effect: The power to regulate it between the states is a unit, but the states may legislate with regard to it in view of local needs and circumstanc es where particular subjects within its op eration do not require the application of a general or uniform system, but where the subject does require a uniform system, as between the states, the power is exclusively in congress and cannot be encroached upon by the states. In that very leading ease it was held that the right of importation of intoxicating liquors from one state to an other includes the right of sale in the origi nal packages at the place where the im portation terminates ; so also ; Lyng v. Mich igan, 135 U. S. 161, 10 Sup. C. 725, 34 L. Ed. 150.