Defendant in error, to sustain her contention that the record does not show notice to her of the proposed work, says that it shows only that a 'parcel' was mailed to her, not a letter, and that the contents of the parcel are not disclosed. To the extreme technicality of this contention the court of appeals answered that no objection was made to the return, and that it averred that the officers and agents of the District made diligent search for defendant in error in the District, and that she could not be found there, and that plaintiff in error believed that she was a citizen and resident of the state of Maryland. The court also pointed out that the return alleged that notice was given to her by publication, as required by the act of Congress, and by registered letter, postage prepaid, which was received by her. A registry return receipt, with her signature attached thereto, was made part of the return. Commenting on this, the court said that, if there was a defect in the return, it was purely technical, and could have been corrected. 'Upon the granting of the writ,' the court observed, 'had objection been made to the adoption by the commissioners of their preliminary return, the court undoubtedly would have permitted an amendment to the record for the purpose of supplying the defects now complained of by petitioner [defendant in error here]. Having, then, made no objection to the form of the return, it is too late to do so now.' If we could concede that the record justifies the distinction made by defendant in error between a parcel and a letter, we should adopt without hesitation the reply made by the court of appeals to the contention based on that distinction, or upon any defect in the return which could have been removed if objection had been seasonably made.

The second contention of defendant in error is that the record fails to disclose that any nuisance existed on her property, or that the means of drainage already there was unsanitary or insufficient, or that any necessity existed for making the connection. This contention seems to be made in this court for the first time. It certainly received no notice from the court of appeals, and the fact that it assumes that there was means of drainage on defendant in error's lot is not alleged in her petition. But, suppose the fact had been alleged; a property owner cannot urge against the drainage system of the District that he had adopted a system of his own, and challenge a comparison with that of the District, and obey or disobey the law according to the result of the comparison. The contention virtually denies any power in Congress to create a system of drainage to which a lot owner must conform.

Finally, defendant in error attacks the validity of the law, and bases attack, to use her words, 'upon certain salient vices in the act which are apparent on its face, of which the principal are —

'(a) The attempt to give controlling evidential effect to the mere existence of an improvement in case of improved property, and to the ex parte certificate of the health officer in the case of unimproved property, thus violating the 'due process' clause of the Constitution.

'(b) Because the act lacks the requisite uniformity, inasmuch as it undertakes to provide one law for property of residents and another for property of nonresident owners in said District.

'(c) Because the act is not capable of universal enforcement, and creates unequal burdens.

'(d) Because the act is incapable of uniform enforcement as against all property in the District of Columbia.'

The first objection was not expressed in the petition nor made in the lower courts, and we might therefore decline to entertain it. At best, defendant in error can only be heard against 'the evidential effect of the mere existence of an improvement,' because her property does not come within the category of unimproved property. Her improvements are dwelling houses, and their mere existence indicated the necessity for drainage. That they may sometimes be vacant is unimportant. What rights owners of lots differently improved or owners of unimproved property may have is no concern of defendant in error. Her contention, therefore, that the act deprives her of due process of law, is unsound.

The other objections expressed the same fundamental idea; to wit, that the act discriminates between resident and nonresident owners of property, and, because it does, it is void. The court of appeals yielded to this contention, following the authority of McGuire v. District of Columbia, 24 App. D. C. 22, 65 L.R.A. 430.

The defendant in error asserts this discrimination and argues its consequences at some length, but does not refer to any provision of the Constitution of the United States which prohibits Congress from enacting laws which discriminate in their operation between persons or things. If there is no express prohibition of such power, may prohibition be implied from our form of government? Upon that proposition we need not express an opinion. If prohibition exists, it must rest on all the powers conferred by the Constitution. This court, however, has just held, in the case of United States ex rel. Atty. Gen. v. Delaware & H. Co. 213 U. S. 366, 53 L. ed. ——, 29 Sup. Ct. Rep. 527, that Congress may, in the exercise of the powers to regulate commerce among the states, discriminate between commodities and between carriers engaged in such commerce. And it was said that the assertion that 'injustice and favoritism' might 'be operated thereby,' could 'have no weight in passing upon the question of power.' In the case at bar we are dealing with an exercise of the police power,—one of the most essential of powers, at times the most insistent, and always one of the least limitable of the powers of government.

However, the question of the power of Congress, broadly considered, to discriminate in its legislation, is not necessary to decide, for, whether such power is expressly or impliedly prohibited, the prohibition cannot be stricter or more extensive than the 14th Amendment is upon the states. That amendment is unqualified in its declaration that a state shall not 'deny to any person within its jurisdiction the equal protection of the laws.' Passing on that amendment, we have repeatedly decided—so often that a citation of the cases is unnecessary—that it does not take from the states the power of classification. And also that such classification need not be either logically appropriate or scientifically accurate. The problems which are met in the government of human beings are different from those involved in the examination of the objects of the physical world, and assigning them to their proper associates. A wide range of discretion, therefore, is necessary in legislation to make it practical, and we have often said that the courts cannot be made a refuge from ill-advised, unjust, or oppressive laws. Billings v. Illinois, 188 U. S. 97, 47 L. ed. 400, 23 Sup. Ct. Rep. 272; Heath & M. Mfg. Co. v. Worst, 207 U. S. 338, 52 L. ed. 236, 28 Sup. Ct. Rep. 114. In the light of these principles the contentions of defendant in error must be judged. The act in controversy makes a distinction in its provision between resident and nonresident lot owners, but this is a proper basis for classification. Regarded abstractly as human beings, regarded abstractly as lot owners, no legal difference may be observed between residents and nonresidents; but, regarded in their relation to their respective lots under regulating laws, the limitations upon jurisdiction, and the power to reach ond and not the other, important differences immediately appear. We said in St. John v. New York, 201 U. S. at page 637 50 L. ed. 898, 26 Sup. Ct. Rep. 554, not only the purpose of a law must be considered, but the means of its administration, the ways it may be defeated. Legislation, to be practical and efficient, must regard this special purpose as well as the ultimate purpose. This was in effect repeated in Field v. Barber Asphalt Paving Co. 194 U. S. 618, 48 L. ed. 1142, 24 Sup. Ct. Rep. 784, where a privilege to protest against a street improvement, given by the statute assailed to resident property owners and denied to nonresident property owners, was sustained, and the statute held not to violate the equality clause of the 14th Amendment. See Travellers' Ins. Co. v. Connecticut, 185 U. S. 364, 46 L. ed. 949, 22 Sup. Ct. Rep. 673.

It is not contended that the act of Congress is not impartial within the classes. The act treats all resident lot owners alike and all nonresidents alike. It is contended that there is a difference in the procedure prescribed in case of default, and nonresident lot owners are thereby discriminated against, though they stand in the same relation to the purpose of the law as resident lot owners. In other words, nonresident lot owners are not treated the same as resident owners in like situation, because against resident owners the coercion of the law is by criminal punishment, while against nonresident owners the remedy is by civil proceedings,—the District does the work that the nonresident owners neglect, and charges the expense thereof on their property. This is a distinction, a discrimination, it may be called, but it has even more justification than that sustained in Field v. Barber Asphalt Paving Co. supra. The statute under consideration in the case at bar enjoins a duty on both resident and nonresident lot owners,—a duty necessary to be followed to preserve the health of the city. There is a difference only in the manner of enforcing it,—a difference arising from the different situation of the lot owners, and therefore competent for Congress to regard in its legislation. In other words, under the circumstances presented by this record, the distinction between residents and nonresidents is a proper basis for classification. It might not be under other circumstances. Blake v. McClung, 172 U. S. 239, 43 L. ed. 432, 19 Sup. Ct. Rep. 165; Blake v. McClung, 176 U. S. 59, 44 L. ed. 371, 20 Sup. Ct. Rep. 307; Sully v. American Nat. Bank, 178 U. S. 289, 44 L. ed. 1072, 20 Sup. Ct. Rep. 935.

That the remedy in the statute under consideration against nonresident owners may be more efficient—more completely fulfil the purpose of the law—than that against resident owners, is beside the question. Indeed, the fact may be disputed. Usually the most emphatic and efficient enforcement of a law is through criminal prosecution. At any rate, it is hard to believe that there will be many resident lot owners whose delinquency under the statute will be so resolute that it will stand against repeated charges of crime and the consequent penalties. But, be that as it may, it was for Congress to decide whether such possibility should be risked rather than incur the greater possibility of more delinquents in so numerous a class as resident lot owners if the District was to first bear the expense of the drainage, and collect it afterward by civil proceedings.

Other criticisms are made of the law to display what is alleged to be its lack of uniformity. For instance, a supposition is made of tenants in common, some of whom are residents and the others nonresidents, and the possible difficulties that may arise from such ownership under the act; and it is asked if the property belongs to resident minors or insane persons, or persons under legal disabilities, can the act be enforced against them or against their property? To these suppositions and questions we answer that it will be time enough to reply when a case arises in which they are presented, and to determine then the operation of the act upon the persons enumerated.

Judgment reversed with directions to reverse the judgment of the Supreme Court, quashing the tax, and to dismiss the petition.

Mr. Justice White did not hear the argument, and took no part in the decision.