The principle of equality of all men before the law (see above, § 204), which is fundamental in our constitutional system, necessarily involves all that is especially guaranteed by the provisions of the Fourteenth Amendment with reference to the equal protection of the laws, and the significance of that provision is that it gives to this guaranty the sanction of the federal constitution and makes it binding on the states so that the persons who are entitled to the equal protection of the law are not left dependent upon the guaranties found in the state constitutions and the enforcement of these guaranties by the state courts, but may rely upon the federal constitution and the protection of the federal courts. It is to be noticed, however, as has already been suggested with reference to due process of law, that the limitation of Amendment XIV is upon state action and not upon individual action. As between individuals the sovereign authority for the protection of rights is in the state governments; it is only as against the action of some department of a state government or its officers in the exercise of public authority that equality before the law is guaranteed by the federal constitution.

The equal protection of the laws does not require that all laws be equally applicable to all persons and all conditions. In the chapter on the police power (see above, § 48) it has been already pointed out that the necessity of regulation may exist as to one class of persons rather than another and as to some conditions rather than others. A law may properly be passed regulating innkeepers which does not apply to those who keep boarding-houses or restaurants; or applying to public carriers of passengers or goods, and not to private carriers. Restrictions on sales of intoxicating liquors may be imposed which are not applicable to sales of other goods. Particular occupations, although they may not be charged with a public interest, such as those of peddlers, pawnbrokers, or dealers in explosives, may be especially regulated in the public interest. Persons pursuing certain professions such as the practice of law, medicine, and pharmacy may be required to have certain qualifications. The requirement of the equal protection of the law is that in imposing regulations on one class of persons which are not imposed on others the distinction must be founded on some reasonable ground of public policy or general welfare and that it be not arbitrary or oppressive. The ground of distinction must have some foundation in reason according to general common sense and good judgment, and the laws applicable to a particular class must not bear more severely upon that class than the reason which justifies that distinction fairly warrants.

It rests primarily with the legislative power to determine what classification and distinctions shall be made and what restrictions shall be imposed; but it is for the courts to determine ultimately whether there is a fair and reasonable ground for such classification and distinctions and whether the restrictions fairly represent the requirements of sound public policy. The courts will, however, only interfere when the legislative department has clearly and plainly exceeded its authority. For instance, it has been held that a regulation requiring that the laundry business within the thickly settled portions of a city shall not be conducted in wooden buildings is valid, because such a regulation is for the protection of the people from the danger of the spread of fire from such establishments (Barrier v. Connolly), but that the restriction of the laundry business to certain classes of persons is unconstitutional because it is not founded upon any reasonable ground as to the qualification of different classes of persons to pursue that particular business (Yick Wo v. Hopkins). Illustrations might be multiplied but without further amplification these suggestions will indicate the principles to be observed in regard to class legislation. It is always to be borne in mind that primarily and fundamentally each person is to be allowed to pursue that calling or line of business which he desires to follow and shall be prevented from doing so only for some sound reason of public policy.