The plaintiff in error was an employee of the Post Office Department of the United States, and while driving a government motor truck in the transportation of mail over a post road from Mt. Airy, Maryland, to Washington, was arrested in Maryland, and was tried, convicted and fined for so driving without having obtained a license from the State. He saved his constitutional rights by motion to quash, by special pleas which were overruled upon demurrer and by motion in arrest of judgment. The facts were admitted and the naked question is whether the State has power to require such an employe to obtain a license by submitting to an examination concerning his competence and paying three dollars, before performing his official duty in obedience to superior command.

The cases upon the regulation of interstate commerce can not be relied upon as furnishing an answer. They deal with the conduct of private persons in matters in which the States as well as the general government have an interest and which would be wholly under the control of the States but for the supervening destination and the ultimate purpose of the acts. Here the question is whether the State can interrupt the acts of the general government itself. With regard to taxation, no matter how reasonable, or how universal and undiscriminating, the State's inability to interfere has been regarded as established since McCulloch v. Maryland, 4 Wheat. 316, 4 L. Ed. 579. The decision in that case was not put upon any consideration of degree but upon the entire absence of power on the part of the States to touch, in that way at least, the instrumentalities of the United States; 4 Wheat. 429, 430, 4 L. Ed. 579; and that is the law today. Farmers' & Mechanics' Savings Bank v. Minnesota, 232 U. S. 516, 525, 526, 34 Sup. Ct. 354, 58 L. Ed. 706. A little later the scope of the proposition as then understood was indicated in Osborn v. Bank of the United States, 9 Wheat. 738, 867 (6 L. Ed. 204)——

'Can a contractor for supplying a military post with provisions, be restrained from making purchases within any State, or from transporting the provisions to the place at which the troops were stationed? or could he be fined or taxed for doing so? We have not yet heard these questions answered in the affirmative.'

In more recent days the principle was applied when the governor of a soldier's home was convicted for disregard of a state law concerning the use of oleomargarine, while furnishing it to the inmates of the home as part of their rations. It was said that the Federal officer was not 'subject to the jurisdiction of the State in regard to those very matters of administration which are thus approved by Federal authority.' Ohio v. Thomas, 173 U. S. 276, 283, 19 Sup. Ct. 453, 455 (43 L. Ed. 699). It seems to us that the foregoing decisions establish the law governing this case.

Of course an employee of the United States does not secure a general immunity from state law while acting in the course of his employment. That was decided long ago by Mr. Justice Washington in United States v. Hart, Pet. C. C. 390, Fed. Cas. No. 15,316; 5 Op. Attys. Gen. 554. It very well may be that, when the United States has not spoken, the subjection to local law would extend to general rules that might affect incidentally the mode of carrying out the employment—as, for instance, a statute or ordinance regulating the mode of turning at the corners of streets. Commonwealth v. Closson, 229 Mass. 329, 118 N. E. 653, L. R. A. 1918C, 939. This might stand on much the same footing as liability under the common law of a state to a person injured by the driver's negligence. But even the most unquestionable and most universally applicable of state laws, such as those concerning murder, will not be allowed to control the conduct of a marshal of the United States acting under and in pursuance of the laws of the United States. Exparte Neagle, 135 U. S. 1, 10 Sup. Ct. 658, 34 L. Ed. 55.

It seems to us that the immunity of the instruments of the United States from state control in the performance of their duties extends to a requirements that they desist from performance until they satisfy a state officer upon examination that they are competent for a necessary part of them and pay a fee for permission to go on. Such a requirement does not merely touch the Government servants remotely by a general rule of conduct; it lays hold of them in their specific attempt to obey orders and requires qualifications in addition to those that the Government has pronounced sufficient. It is the duty of the Department to employ persons competent for their work and that duty it must be presumed has been performed. Keim v. United States, 177 U. S. 290, 293, 20 Sup. Ct. 574, 44 L. Ed. 774.

Judgment reversed.

Mr. Justice PITNEY and Mr. Justice McREYNOLDS dissent.