Opinion of the Court. A leading case upon the subject is that of Morgan v. Loui siana, 118 U. S. 455, 463-465, which related to certain quarantine laws of Louisiana, the validity of which were questioned partly upon the ground that they were inconsistent with the power of Congress to regulate commerce among the States. This court said: "Is the law under consideration void as a regulation of commerce? Undoubtedly it is in some sense a regulation of commerce. It arrests a vessel on a voyage which may have been a long one. It may affect commerce among the States when the vessel is coming from some other State of the Union than Louisiana, and it may affect commerce with foreign nations when the vessel arrested comes from a foreign port. This interruption of the voyage may be for days or weeks. It extends to the vessel, the cargo, the officers and seamen and the passengers. In so far as it provides a rule by which this power is exercised, it cannot be denied that it regulates commerce. We do not think it necessary to enter into the inquiry whether, notwithstanding this, it is to be classed among those police powers which were retained by the States as exclusively their own, and, therefore, not ceded to Congress. For, while it may be a police power in the sense that all provisions for the health, comfort and security of the citi zens are police regulations, and an exercise of the police power, it has been said more than once in this court that, even where such powers are so exercised as to come within the domain of Federal authority as defined by the Constitution, the latter must prevail. Gibbons v. Ogden, 9 Wheat. 1, 210; Henderson v. The Mayor, 92 U. S. 259, 272; New Orleans Gas Co. v. Louisiana Light Co., 115 U. S. 650, 661. But it may be conceded that whenever Congress shall undertake to provide for the commercial cities of the United States a general system of quarantine, or shall confide the execution of the details of such a system to a National Board of Health, or to local boards, as may be found expedient, all state laws on the subject will be abrogated, at least so far as the two are inconsistent. But, until this is done, the laws of the State on the subject are valid." Again: "Quarantine laws belong to that class of state legislation which, whether passed with intent to Opinion of the Court. regulate commerce or not, must be admitted to have that effect, and which are valid until displaced or contravened by some legislation of Congress." Upon the subject of legislation enacted under the police power of a State, and which, although affecting more or less commerce among the States, was adjudged to be valid, until displaced by some act of Congress, the case of Smith v. Alabama, 124 U. S. 465, 474, 479, 482, is instructive. A statute of Alabama made it unlawful for an engineer on a railroad train in that State to operate an engine upon the main line of the road used for the transportation of passengers or freight, without first undergoing an examination and obtaining a license from a State Board of Examiners. The point was made that the statute, in its application to engineers on interstate trains, was a regulation of commerce among the States, and repugnant to the Constitution. This court referred to and reaffirmed the principle announced in Sherlock v. Alling, 93 U. S. 99, 102, where it was said: "In conferring upon Congress the regulation of commerce, it was never intended to cut the States off from legislating on all subjects relating to the health, life and safety of their citizens, though the legislation might indirectly affect the commerce of the country. Legisla tion, in a variety of ways, may affect commerce and persons engaged in it without constituting a regulation of it within the meaning of the Constitution." Referring to the fact that Congress had prescribed the qualifications for pilots and engineers of steam vessels engaged in the coasting trade and navigating the inland waters of the United States, while engaged in commerce among the States, the court, in Smith v. Alabama, said that the power of Congress "might, with equal authority, be exercised in prescribing the qualifications for locomotive engineers employed by railroad companies engaged in the transportation of passengers and goods among the States, and in that case would supersede any conflicting provisions on the same subject made by local authority. But the provisions on the subject contained in the statute of Alabama under consideration are not regulations of interstate commerce. It is a misnomer to call them such. Considered in themselves they Opinion of the Court. are parts of that body of the local laws which, as we have already seen, properly governs the relation between carriers of passengers and merchandise and the public who employ them, which are not displaced until they come in conflict with express enactments of Congress in the exercise of its power over commerce, and which, until so displaced, according to the evident intention of Congress, remain as the law governing carriers in the discharge of their obligations, whether engaged in the purely internal commerce of the State or in commerce among the States. No objection to the statute, as an impediment on the free transaction of commerce among the States, can be found in any of its special provisions." Again: "We find, therefore, first, that the statute of Alabama, the validity of which is under consideration, is not, considered in its own nature, a regulation of interstate commerce, even when applied as in the case under consideration; secondly, that it is properly an act of legislation within the scope of the admitted power reserved to the State to regulate the relative rights and duties of persons being and acting within its territorial jurisdiction, intended to operate so as to secure for the public safety of persons and property; and, thirdly, that, so far as it affects transactions of commerce among the States, it does so indirectly, incidentally and remotely, and not so as to burden or impede them, and, in the particulars in which it touches those transactions at all, it is not in conflict with any express enactment of Congress on the subject, nor contrary to any intention of Congress to be presumed from its silence." So in Nashville etc. Railway v. Alabama, 128 U. S. 96, 99, -101, which involved the validity of a state enactment which, for the protection of the travelling public, declared any one disqualified from serving on railroad lines within the State who had color blindness and defective vision, and which statute was equally applicable to domestic and interstate railroad trains, the court said: "It is conceded that the power of Congress to regulate interstate commerce is plenary; that, as incident to it, Congress may legislate as to the qualifications, duties and liabilities of employés and others on railway trains engaged in that commerce; and that such legislation will Opinion of the Court. supersede any state action on the subject. But until such legislation is had, it is clearly within the competency of the States to provide against accidents on trains whilst within their limits. Indeed, it is a principle fully recognized by decisions of state and Federal courts that wherever there is any business in which, either from the products created or the instrumentalities used, there is danger to life or property, it is not only within the power of the States, but it is among their plain duties, to make provision against accidents likely to follow in such business, so that the dangers attending it may be guarded against so far as is practicable." Referring to some observations made in Smith v. Alabama, supra, the court said: "The same observations may be made with respect to the provisions of the state law for the examination of parties to be employed on railways with respect to their powers of vision. Such legislation is not directed against commerce, and only affects it incidentally, and therefore cannot be called, within the meaning of the Constitution, a regulation of commerce." These authorities make it clear that the legislative enactments of the States, passed under their admitted police powers, and having a real relation to the domestic peace,.order, health and safety of their people, but which, by their necessary operation, affect to some extent, or for a limited time, the conduct of commerce among the States, are yet not invalid by force alone of the grant of power to Congress to regulate such commerce; and, if not obnoxious to some other constitutional provision or destructive of some right secured by the fundamental law, are to be respected in the courts of the Union until they are superseded and displaced by some act of Congress passed in execution of the power granted to it by the Constitution. Local laws of the character mentioned have their source in the powers which the States reserved and never surrendered to Congress, of providing for the public health, the public morals and the public safety, and are not, within the meaning of the Constitution, and considered in their own nature, regulations of interstate commerce simply because, for a limited time or to a limited extent, they cover Dissenting Opinion: Chief Justice, White, J. the field accupied by those engaged in such commerce. The statute of Georgia is not directed against interstate commerce. It establishes a rule of civil conduct applicable alike to all freight trains, domestic as well as interstate. It applies to the transportation of interstate freight the same rule precisely that it applies to the transportation of domestic freight. And it places the business of transporting freight in the same category as all other secular business. It simply declares that, on and during the day fixed by law as a day of rest for all the people within the limits of the State from toil and labor incident to their callings, the transportation of freight shall be suspended. We are of opinion that such a law, although in a limited degree affecting interstate commerce, is not for that reason a needless intrusion upon the domain of Federal jurisdiction, nor strictly a regulation of interstate commerce, but, considered in its own nature, is an ordinary police regulation designed to secure the well-being and to promote the general welfare of the people within the State by which it was established, and, therefore, not invalid by force alone of the Constitution of the United States. The judgment is Affirmed. The CHIEF JUSTICE, with whom concurred MR. JUSTICE WHITE, dissenting: Intercourse and trade between the States by means of railroads passing through several States, is a matter national in its character and admitting of uniform regulation. The power of Congress to regulate it is exclusive and under the Constitution it is free and untrammelled except as Congress otherwise provides. This statute in requiring the suspension of interstate commerce for one day in the week amounts to a regulation of that commerce, and is invalid because the power of Congress in that regard is exclusive. But it is said that the act is not a regulation of commerce but a mere regulation of police, and that the so called police power of a State is plenary. The result, however, is the same. When a power of a State and |