In an earlier chapter of this treatise it has been pointed out that the courts will not by mandamus or other writ attempt to control the exercise by executive or administrative agents of a discretion given them by the Constitution or statutes. This, as we have seen, excludes from the field of judicial review all those acts which, as political in character, are purely discretionary. It also excludes an attempt upon the part of the courts to control all other administrative and executive acts in so far as there is possessed by those officials intrusted with their performance, a discretion as to how the acts shall be performed at all. Where, however, an act, not purely political in character, is by law required of an officer, the performance of which involves the exercise of a discretion, the courts may require that that discretion be exercised and the act performed. Furthermore, whether or not an officer has overstepped the limits of the discretionary powers granted him is always a proper subject for judicial determination.

33 187 U. S. 94; 23 Sup. Ct. Rep. 33; 47 L. ed. 90.

That a mandamus will lie to compel the performance of purely ministerial acts, that is, those not involving the exercise of political or administrative discretion, is a principle that antedates the adoption of the United States Constitution.