A ministerial duty, the performance of which may, in proper cases, be required of the head of a department, by judicial process, is one in which respect to nothing is left to discretion. It is a simple, definite duty, arising under conditions admitted or proved to exist, and imposed by law.[238] This means that where the law requires the performance of a single specific act, there is no room for the exercise of judgment, there is nothing left to discretion; the act is ministerial. “Very different is the duty of the President in the exercise of the power to see that the laws are faithfully executed,—the duty thus imposed is in no sense ministerial; it is purely executive and political.”[239] In application of this principle The Congress is the legislative department of the government; the President is the executive department. Neither can be restrained in its action by the judicial department; though the acts of both, when performed, are, in proper cases, subject to cognizance.[240] 95. The principle applies alike to the States. The control of the exercise of powers belonging exclusively to the executive department of the government of a State can in no sense or degree be assumed by either of the other departments, as such control would amount to the performance of executive duties by the legislative or the judiciary, a confusion of functions distinctly forbidden by the constitution. And it has been decided that “_mandamus_ will not issue to the Governor to compel the performance of _any_ duty pertaining to his office, whether political or merely ministerial; whether commanded by the constitution or by some law passed on the subject.”[241] The principle of American constitutional law as to executive and ministerial powers is thus stated: The Court will not interfere by _mandamus_ with the executive officers of the government in the exercise of their ordinary official duties, even where those duties require an interpretation of the law, the Court having no appellate power for that purpose; but when they refuse to act in a case at all, or when by special statute, or otherwise, a more ministerial duty is imposed upon them, that is, a service which they are bound to perform without further question, then, if they refuse, a _mandamus_ may be issued to compel them.[242]