Opinion of the Court. hereby empowered to order and require that any premises, farm, or farms where such disease exists, or has existed, be put in quarantine; to order all or any animals coming into the District to be detained at any place or places for the purpose of inspection and examination; to prescribe regulations for and to require the destruction of animals affected with contagious, infectious, or communicable disease, and for the proper disposition of their hides and carcasses; to prescribe regulations for disinfection, and such other regulations as they may deem necessary to prevent infection or contagion being communicated, and shall report to the Commissioner of Agriculture whatever they may do in pursuance of the provisions of this section. 66 "§ 9. That it shall be the duty of the several United States district attorneys to prosecute all violations of this act which shall be brought to their notice or knowledge by any person making the complaint under oath; and the same shall be heard before any District or Circuit Court of the United States or territorial court holden within the district in which the violation of this act has been committed." 23 Stat. 31, c. 60. It may be here stated that by the act of February 9, 1889, the Department of Agriculture was made one of the Executive Departments of the Government, and placed under the supervision and control of a Secretary of Agriculture, 25 Stat. 659, c. 122; and that by the act of July 14, 1890, the Secretary was vested with all the authority which by the above act of May 29, 1884, was conferred upon the Commissioner of Agriculture, 26 Stat. 282, 288, c. 707. It is quite true, as urged on behalf of the defendant, that the transportation of live stock from State to State is a branch of interstate commerce and that any specified rule or regulation in respect of such transportation, which Congress may lawfully prescribe or authorize and which may properly be deemed a regulation of such commerce, is paramount throughout the Union. So that when the entire subject of the transportation of live stock from one State to another is taken under direct national supervision and a system devised by which diseased stock may be excluded from interstate commerce, all Opinion of the Court. local or State regulations in respect of such matters and covering the same ground will cease to have any force, whether formally abrogated or not; and such rules and regulations as Congress may lawfully prescribe or authorize will alone control. Gibbons v. Ogden, 9 Wheat. 1, 210; Morgan v. Louisiana, 118 U. S. 455, 464; Hennington v. Georgia, 163 U. S. 299, 317; N. Y., N. H. & H. R. R. Co. v. New York, 165 U. S. 628, 631; Missouri, Kansas & Texas Railway Co. v. Haber, 169 U. S. 613, 626; Rasmussen v. Idaho, 181 U. S. 198, 200. The power which the States might thus exercise may in this way be suspended until national control is abandoned and the subject be thereby left under the police power of the States. But the difficulty with the defendant's case is that Congress has not by any statute covered the whole subject of the transportation of live stock among the several States, and, except in certain particulars not involving the present issue, has left a wide field for the exercise by the States of their power, by appropriate regulations, to protect their domestic animals against contagious, infectious and communicable diseases. An examination of the Animal Industry Act will make this entirely clear. Three distinct subjects are embraced by that act. One is the ascertainment through the Agricultural Department of the condition of the domestic animals of the United States, the causes of contagious, infectious or communicable diseases affecting them, the best methods for treating, transporting and caring for animals, the means to be adopted for the suppression and extirpation of such diseases, particularly that of contagious pleuro-pneumonia, and to collect such information on those subjects as will be valuable to the agricultural and commercial interests of the country. Congress did not assume to declare that "the rules and regulations" which that Department might adopt as necessary "for the speedy and effectual suppression and extirpation of said diseases" should have in themselves, or apart from the action of a State, any binding force upon the States. They were to be certified to the executive authority of each State, and the coöperation of such authorities in executing the act of Congress invited. If the authorities of any State Opinion of the Court. adopted the plans and methods devised by the Department, or if the State authorities adopted measures of their own which the Department approved, then the money appropriated by Congress could be used in conducting the required investigations and in such disinfection and quarantine measures as might be necessary to prevent the spread of the diseases in question from one State or Territory into another. Congress did not intend to override the power of the States to care for the safety of the property of their peoples by such legislation as they deemed appropriate. It did not undertake to invest any officer or agent of the Department with authority to go into a State and without its assent take charge of the work of suppressing or extirpating contagious, infectious or communicable diseases there prevailing and which endangered the health of domestic animals. Nor did Congress give the Department authority by its officers or agents to inspect cattle within the limits of a State and give a certificate that should be of superior authority in that or other States, or which should entitle the owner to carry his cattle into or through another State without reference to the reasonable and valid regulations which the latter State may have adopted for the protection of its own domestic animals. It should never be held that Congress intends to supersede or by its legislation suspend the exercise of the police powers of the States, even when it may do so, unless its purpose to effect that result is clearly manifested. This court has said-and the principle has been often reaffirmed that "in the application of this principle of supremacy of an act of Congress in a case where the State law is but the exercise of a reserved power, the repugnance or conflict should be direct and positive, so that the two acts could not be reconciled or consistently stand together." Sinnot v. Davenport, 22 How. 227, 243. The certificate given to the defendant by Assistant Inspector Hart of the Bureau of Animal Industry was in itself without legal weight in Colorado. As said in Missouri, Kansas & Texas Railway Company v. Haber, above cited: "While the States were invited to coöperate with the General Government in the execution and enforcement of the act, whatever power they had to protect their domestic cattle against such diseases was left untouched and un Opinion of the Court. impaired by the act of Congress." Hence, it was decided in that case that the Animal Industry Act did not stand in the way of the State of Kansas enacting a statute declaring that any person driving, shipping or transporting, or causing to be shipped, driven or transported into or through that State, any cattle liable or capable of communicating Texas or splenetic fever to domestic cattle should be liable to the person injured thereby for all damages sustained by reason of the communication of said disease or fever, to be recovered in a civil action. We there held that the Kansas statute did nothing more than establish a rule of civil liability, in that State, affected no regulation of interstate commerce that Congress had prescribed or authorized, and impaired no right secured by the National Constitution. Another subject embraced by the act of Congress related to the exportation from ports of the United States to ports in foreign countries of live stock affected with contagious, infectious or communicable diseases, especially pleuro-pneumonia; and in relation to that matter the Secretary of the Treasury was authorized to take such steps and adopt such measures not inconsistent with the act of Congress, as he deemed necessary. As the present case is not one of the exportation of live stock to a foreign country, it is unnecessary to consider what power, if any, remained with the States, after the passage of the Animal Industry Act, to suppress or extirpate diseases that in fact affected live stock, which it was the purpose of the owners to export. Still another subject covered by the act is the driving on foot or transporting from one State or Territory into another State or Territory, or from any State into the District of Columbia, or from the District into any State, of any live stock known to be affected with any contagious, infectious or communicable disease. But this provision does not cover the entire subject of the transporting or shipping of diseased live stock from one State to another. The owner of such stock, when bringing them into another State, may not know them to be diseased; but they may, in fact, be diseased, or the circumstances may be such as fairly to authorize the State into which Opinion of the Court. they are about to be brought to take such precautionary measures as will reasonably guard its own domestic animals against danger from contagious, infectious or communicable diseases. The act of Congress left the State free to cover that field by such regulations as it deemed appropriate, and which only incidentally affected the freedom of interstate commerce. Congress went no farther than to make it an offence against the United States for any one knowingly to take or send from one State or Territory to another State or Territory, or into the District of Columbia, or from the District into any State, live stock affected with infectious or communicable disease. The Animal Industry Act did not make it an offence against the United States to send from one State into another live stock which the shipper did not know were diseased. The offence charged upon the defendant in the State court was not the introduction into Colorado of cattle that he knew to be diseased. He was charged with having brought his cattle into Colorado from certain counties in Texas, south of the 36th parallel of north latitude, without said cattle having been held at some place north of said parallel of latidude for at least the time required prior to their being brought into Colorado, and without having procured from the State Veterinary Sanitary Board a certificate or bill of health to the effect that his cattle-in fact-were free from all infectious or contagious diseases, and had not been exposed at any time within ninety days prior thereto to any such diseases, but had declined to procure such certificate or have the inspection required by the statute. His knowledge as to the actual condition of the cattle was of no consequence under the State enactment or under the charge made. Our conclusion is that the statute of Colorado as here involved does not cover the same ground as the act of Congress and therefore is not inconsistent with that act; and its constitutionality is not to be questioned unless it be in violation of the Constitution of the United States, independently of any legislation by Congress. The latter question we now proceed to examine. Certain principles are well settled by the former decisions of this court. One is that the purpose of a statute, in whatever language it may be framed, must be determined by its natural |