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 QUARANTINE LAWS. 2/9

straintS amounting even to a temporary prohibition of intercourse. So far as they do not regulate commerce, they are worthless for the protection of health. It is hard to conceive rules exercising more direct control over commerce. " Transportation is essential to commerce, or, rather, it is commerce itself ; and every obstacle to it or burden laid upon it by legislative authority iS' regula- tion." ^

In discussing regulations of commerce, there is great danger of being misled by terms, for different judges have not used the words in the same sense. Upon the meaning of the phrase ** to regulate commerce *' in the Constitution, the decisions have in- deed substantially agreed. The words are not used in a technical sense. *' To regulate," said Chief Justice Marshall in Gibbons v, Ogden is "to prescribe the rules by which commerce is to be governed." 2 "That is," adds Mr. Justice Field, "the condition upon which it shall be conducted ; to determine how far it shall be free and untrammeled, how far it shall be burdened by duties and imposts, and how far it shall be prohibited." ^ To exercise control over commerce seems to be what is meant. The idea to be contrasted with regulating is affecting or influencing com- merce. Commerce is so sensitive a thing that scarcely a law can be passed that does not more or less remotely affect it. Laws not otherwise unconstitutional, which operate on foreign or interstate commerce only indirectly, secondarily, and remotely, have never been treated by the courts as forbidden to the States.* To this class belong most, but not all. State police regulations. " In con- ferring upon Congress the regulation of commerce, it was never intended to cut the States off from legislating on all subjects re- lating to the health, life, and safety of their citizens, though the legislation might indirectly affect the commerce of the country. Legislation, in a great variety of ways, may affect commerce and persons engaged in it without constituting a regulation of it

1 R. R. Co. V, Husen, 95 U S. 465, 470, citing other cases.

«9 Wheat, 1, 196 (1824).

» Wclton V, State of Missouri, 91 U. S. 275, 279 (1875).

collected in Mr. Pomeroy's article upon The Power of Congress to Regulate Interstate Commerce, 4 South L^wRer. 357, 390, et seq.\ also in Phila. Steamship Co. v. PennsyU Tania, 122 U. S. 336, 346 (1886). A recent case is Smith v. State of Alabama, 8 Sup. Ct. Rep. 564, 124 U. S. 465 (1888). The doctrine is carefully and elaborately stated in Robbins v, Shelby Taxing District, X20 U. S. 489, 493 (1886).
 * The cases establishing this distinction are numerous and uncontroverted. Many are