We do not deem it necessary to the decision of the question raised in this case to determine whether the resignation by the commissioner of his seat in the senate was lawful and valid, and duly vacated his place as a member of that body; nor whether there was a constitutional incompatibility which would prevent him from lawfully holding his two appointments as commissioner, under Sts. 1855, c. 230, and 1856, c. 296, at the same time that he was entitled to claim his rights and perform his duties as a senator. These are interesting and important questions, but they are immaterial to the matter in issue between the parties to this suit.
The commissioner, under whose direction and control the work authorized by St. 1856, c. 296 was done, acted under an appointment made in pursuance of § 8 of that statute, by the governor and council. He was not therefore a mere usurper of or intruder into a public office. He acted under a commission prima facie valid, and issued by an authority apparently empowered to invest him with the legal rights and powers of the office to which he was appointed. If there was any illegality or incompatibility which would incapacitate him from holding the office, it arose from extrinsic facts which did not appear on the face of the commission under which he acted In supervising the work for which reimbursement is sought in this action. He was therefore clearly an officer de facto. The precise definition of an officer de facto is, one who comes in by the forms of law, and acts under a commission or election apparently valid, but, in consequence of some illegality, incapacity or want of qualification, is incapable of lawfully holding the office. The exact distinction between an usurper or intruder and an officer de facto is this : the former has no color of title to the office; the latter has. by virtue of some appointment or election. It follows that the acts of the commissioner cannot be called in question in this suit. They are valid as respects third persons, and cannot be impeached in a collateral way in proceedings to which the officer is not a party. This principle has often been recognized and applied by this court, and quite recently in Coolidge v. Brigham, ante, 333. It is difficult to find a stronger illustration *558of the application of this rule than is furnished by the case of Fowler v. Bebee, 9 Mass. 231, where it was held that the acts of an officer, appointed without any authority of law, could not be invalidated or inquired into in a suit between third persons. See also Bucknam v. Ruggles, 15 Mass. 180. The case of McGregor v. Balch, 14 Verm. 428, is very similar to the one at bar. It was there decided that, under the constitution of the State of Vermont, a person could not hold the office of postmaster under the government of the United States and that of justice of peace under the authority of the state, at the same time; but that his acts as a justice could not be set aside or invalidated in a suit between third persons, notwithstanding this incompatibility. It was urged by the counsel for the defendants, that this well settled principle is not applicable to the present case, because the commissioner was appointed on the application of the plaintiffs, and his duties were confined by law to acts which must operate directly on the rights and property of the party denying his authority. But we can see no foundation for this argument; certainly it is not sustained by the authorities. The cases all recognize the rule as being founded on public policy, which does not allow the title of a person to an office to bt? inquired into and determined in proceedings to which he is not a party; nor the rights of third persons to be affected by illegalities or informalities in the appointment or election of public officers who are acting under color of title. Indeed the rule has been expressly held to apply to all public officers, whatever may be the nature of their duties. Bucknam v. Ruggles, ubi supra. It does not depend on the nature, or extent of their authority or jurisdiction. Certainly in the present case it would work great hardship and injustice, if the plaintiffs were made to forfeit all right to reimbursement for expenses incurred in pursuance of a public statute, and for the mutual benefit of themselves and the defendants, by reason of the irregular or improper action of the executive authority of the state, in making an appointment to the office of commissioner of a person constitutionally disqualified for the place. It is no answer to this suggestion that the appointment was made at *559the request of the plaintiffs. They were expressly authorized by the eighth section of the statute of 1856, c. 296, to make application to the governor for such appointment. But it does not appear that they designated the individual to be appointed, or had anything to do with his selection. On the contrary, the presumption is that the appointment was made by the governor with the consent of his council without any reference to the wishes of the parties concerned, and solely with regard to the public interests involved in the faithful and impartial performance of his duties. Nor can it make any difference that the plaintiffs were informed by the defendants that they denied the authority of the commissioner to perform the duties of his office, by reason of the irregularity and invalidity of his appointment. They were not bound to act or to refrain from action in consequence of such a notice. They had a right to presume that the commissioner, acting under an appointment from the chief magistrate of the state, sanctioned by his constitutional advisers, was rightly in office. It was their duty so to regard him, because, being an officer de facto, he had a right to exercise the authority conferred on him by his appointment. If the defendants doubted the validity of his appointment, or intended to call it in question, they might have resorted to the proper steps to obtain a stay of his proceedings by a quo warranta, filed by the attorney general as the representative of the government, under which the right of the commissioner to his office could be legally tried and adjudicated. Commonwealth v. Fowler, 10 Mass. 290. But they had no right to lie by and permit the plaintiffs to incur large' expenditures under the authority of the commissioner, and seek to' avoid a reimbursement of their share by attempting to impeach and set aside his doings, in a suit brought to recover the amount which they are legally bound to pay. Nonsuit taken off; case to stand for trial.