false statement that the person to whom the warrant was issued has rendered services in teaching, when in fact such person has not rendered any services at all. The question was directly presented in Mayor v. Ray, 19 Wall. 468. In view of the earnestness with which this claim of estoppel was urged, we will quote briefly from this opinion, as accurately expressing our views. Speaking of a similar evidence of indebtedness, the court say: "But every holder of a city order or certificate knows that, to be valid or genuine at all, it must have been issued as a voucher for city indebtedness. It could not be lawfully issued for any other purpose: He must take it, therefore, subject to the risk that it has been lawfully and properly issued. His claim to be a bona fide holder will always be subject to this qualification. The face of the paper itself is notice to him that its validity depends upon the regularity of its issue. The officers of the city have no authority to issue it for any illegal or improper purpose, and their acts cannot create an estoppel against the city itself, its tax-payers, or people." To same effect Wall v. Monroe Co., 103 U. S. 74; Bank v. School Dist., 42 N. W. Rep. 767; 1 Dill. Mun. Corp. (3d Ed.) § 504.
There is no force in the position that the defendant, having received the benefit of the teacher's services, is liable. Such a doctrine would defeat the policy of the law, which is to give the people of the state the benefit of trained and competent teachers. The law recognizes only one evidence that that policy has been regarded—the certificate of qualification. If the defendant could be made liable by the mere receipt of the benefit of the services rendered, the law prohibiting the employment of teachers without certificates, and declaring void all contracts made in contravention of that provision, would be, in effect, repealed, and the protection of the people against incompetent and unfit teachers, which such statute was enacted to accomplish, would be destroyed. Where a contract is void because of the express declaration of a statute, or because prohibited in terms, the retention by a municipality of the fruits of such a contract will not subject it to liability, either under the contract or upon a quantum meruit. Dickinson v. City of Poughkeepsie, 75 N. Y. 65; McBrien v. City of Grand Rapids, 22 N. W. Rep.
