In the case of Osborn v. Bank of the United States30 an injunction was asked of the federal court to restrain the auditor of the State of Ohio from proceeding against the Bank of the United States under a tax law of that State which law, it was alleged, was in violation of the federal Constitution. Among other grounds for resistance to this application it was argued that the actual defendant in interest in the case was the State; that the State was not and could not be made a defendant of record, and that, therefore, its agents might not be restrained. To this Marshall, who rendered the opinion of the court, replied that the direct interest of the State in the suit was admitted, and, also, that under the Eleventh Amendment it could not be made a party of record, but that this did not render the federal court powerless to restrain the State's agents from proceeding under an unconstitutional law against an individual or corporation. In supporting this contention, Marshall, as was his wont, argued not so much from the requirements of technical procedure or from the letter of the Constitution, as from the general character of the government intended to be established and maintained by that instrument, and from the politically inconvenient and destructive results that would follow from an acceptance of the doctrine he was controverting. " A denial of jurisdiction" he said, " forbids all inquiry into the nature of the case. It applies to cases perfectly clear in themselves; to cases where the government is in the exercise of its best established and most essential powers, as well as to whose which may be deemed questionable. It asserts that the agents of a State, alleging the authority of a law void in itself, because repugnant to the Constitution, may arrest the execution of any law in the United States. It maintains that, if a State shall impose a fine or penalty on any person employed in the execution of any law of the United States, it may levy that fine or penalty by a ministerial officer, without the sanction even of its own courts; and that the individual, though he perceives the approaching danger, can obtain no protection from the judicial department of the government. . . . The person thus obstructed in the performance of his duty may indeed resort to his action for damages, after the infliction of the injury, but cannot avail himself of the preventive justice of the nation to protect him in the performance of his duties."

30 9 Wh. 738; 6 L. ed. 204.

In the Osborn case the Supreme Court did not permit a State to interfere with the exercise of the functions of a federal agent and shield itself behind the Eleventh Amendment. In succeeding cases the Supreme Court has in similar manner refused to allow the States, through their respective agents, to interfere with the personal and property rights of private individuals. In some cases it has awarded mandamus to compel the performance by state officials of duties legally imposed upon them. In other cases, it has restrained them by writs of injunction from violating private rights under color of authority derived from unconstitutional laws. Thus in Board of Liquidation v. McComb31 the court said: "A State, without its consent, cannot be sued by an individual, and a court cannot substitute its own discretion for that of executive officers in matters belonging to the proper jurisdiction of the latter. But it has been well settled, that, when a plain official duty, requiring no exercise of discretion, is to be performed, and performance is refused, any person who will sustain personal injury by such refusal may have a mandamus to compel its performance; and when such duty is threatened to be violated by some positive official act, any person who will sustain personal injury thereby, for which adequate compensation cannot be had at law, may have an injunction to prevent it. In such cases, the writs of mandamus and injunction are somewhat correlative to each other. In either case, if the officer plead the authority of an unconstitutional law for the non-performance or violation of his duty, it will not prevent the issuing of the writ. An unconstitutional law will be treated by the courts as null and void."

31 92 U. S. 531; 23 L. ed. 623.

In a number of cases, however, the Supreme Court has not permitted this principle of the legal responsibility of the agents of a State to countenance what is in actual effect a suit not against them personally, but against them officially as agents of the State, and, therefore, in reality against the States themselves whose officials they are. Nor has the court been willing to command the performance by a state official of other than mere ministerial acts in which no official discretion has been involved.