delivered the opinion of the Court:

The interesting constitutional question which was presented with much force and ability by appellant’s counsel should not be considered by us on this appeal. It is conceded by counsel that after the court below dismissed the bill the appellees proceeded with the trial of the appellant on the charges and specifications described, adjudged him guilty, and removed him from his office as supervising principal. The trial sought to be enjoined ended on March 9, 1901, and this appeal came to this court ten days later. When an injunction has been dissolved it cannot be revived except by a new exercise of judicial power; and no appeal by dissatisfied parties can of itself revive it. A fortiori the mere prosecution of an appeal cannot operate as an injunction where none has been granted. Knox County v. Harshman, 132 U. S. 14, 16, 33 L. ed. 249, 250, 10 Sup. Ct. Rep. 8. The things sought to be prohibited have been done, and cannot be undone by any order of this court or the court below. There is nothing but a moot case remaining. Eeversing the decree in this case would be doing a vain thing. A judicial tribunal is to decide actual controversies by a judgment which can be carried into effect, and not to give opinions upon moot questions, or to declare principles of law which cannot affect the matter in issue before it. See United States ex rel. Gannon v. Georgetown College, 28 App. D. C. 91; Mills v. Green, 159 U. S. 651, 653, 40 L. ed. 293, 294, 16 Sup. Ct. Rep. 132.

The decisive action which made this appeal of no effect was taken by the appellees, the present board of education, which succeeded a prior board; and under the act of June 20, 1906, the appellees are at least de facto the board of education. It is made up of members who have discharged the duties of this office since July 3, 1906, when they were appointed by the jus*91tices of the supreme court of this District. The appellant has recognized this board, has taken his oath of office under it, has received his salary under this board’s authorization, the departments of the government recognize this board of education, and the appropriations of Congress have been paid out under its authority. This board succeeded another which did not dispute the lawful succession, and it is now the only board of education in existence in this District. If we could do so, no good reason appears why we should seek to review the proceedings ■of this Board in behalf of the appellant, who has in several ways recognized the existence of this board of education. As Mr. Justice Field said: “Where an office exists under the law, it matters not how the appointment of the incumbent is made, ■so far as the validity of his acts are concerned. It is enough that he is clothed with the insignia of the office, and exercises its powers and functions. * * * The official acts of such persons are recognized as valid on grounds of public policy, and for the protection of those having official business to transact.” Norton v. Shelby County, 118 U. S. 425, 444, 30 L. ed. 178, 187, 6 Sup. Ct Rep. 1121; Crutchfield v. Hewett, 2 App. D. C. 385. It was such a board that found the appellant guilty and dismissed him; and before this appeal came to this court the court below dismissed the bill, the object of which was to restrain this board from proceeding with that trial, and from deciding the case and dismissing the appelant. Accomplished facts have made this a moot question.

This appeal should be dismissed, with costs, and it is so ordered.