general welfare of the public. Both property and liberty are held on such reasonable conditions as may be imposed by the governing power of the state in the exercise of those powers, and with such conditions the Fourteenth Amendment was not designed to interfere. . . .
The state, therefore, has power to prevent the individual from making certain kinds of contracts, and in regard to them the federal Constitution offers no protection. If the contract be one which the state, in the legitimate exercise of its police power, has the right to prohibit, it is not prevented from prohibiting it by the Fourteenth Amendment. Contracts in violation of a statute, either of the federal or state government, or a contract to let one's property for immoral purposes, or to do any other unlawful act, could obtain no protection from the federal Constitution, as coming under the liberty of person or of free contract. Therefore, when the state, by its legislature, in the assumed exercise of its police powers, has passed an act which seriously limits the right to labor or the right of contract in regard to their means of livelihood between persons who are sui juris (both employer and employé), it becomes of great importance to determine which shall prevail -- the right of the individual to labor for such time as he may choose, or the right of the state to prevent the individual from laboring, or from entering into any contract to labor, beyond a certain time prescribed by the state.
This court has recognized the existence and upheld the exercise of the police powers of the states in many cases which might fairly be considered as border ones, and it has, in the course of its determination of questions regarding the asserted invalidity of such statutes, on the ground of their violation of the rights secured by the federal Constitution, been guided by rules of a very liberal nature, the application of which has resulted, in numerous instances, in upholding the validity of state statutes thus assailed. Among the later cases where the state law has been upheld by this court is that of Holden v. Hardy, 169 U.S. 366. A provision in the act of the legislature of Utah was there under consideration, the act limiting the employment of workmen in all underground mines or workings, to eight hours per day, "except in cases of emergency, where life or property is in imminent danger." It also limited the hours of labor in smelting and other institutions for the reduction or refining of ores or metals to eight hours per day, except in like cases of emergency. The act was held to be a valid exercise of police powers of the state. A review of many of the cases on the subject, decided by this and other courts, is given in the opinion. It was held that the kind of employment, mining, smelting, etc., and the character of the employés in such kinds of labor, were such as to make it reasonable and proper for the state to interfere to prevent the employés from being constrained by the rules laid down by the proprietors in regard to labor. . . .
It must, of course, be conceded that there is a limit to the valid exercise of the police power by the state. There is no dispute concerning this general proposition. Otherwise the Fourteenth Amendment would have no efficacy and the legislatures of the states would have unbounded power, and it would be enough to say that any piece of legislation was enacted to conserve the morals, the health, or the safety of the people; such legislation would be valid, no matter how absolutely without foundation the claim might be. The claim of the police power would be a mere pretext, -- become another and delusive name for the supreme sovereignty of the state to