It has already been shown that the States are permitted, in the exercise of the powers reserved to them, substantially to affect interstate and foreign commerce, so long as this interference is an indirect, incidental one, the legislation in question a legitimate and bona fide exercise of a reserved power, and not in contravention to any existing federal statute or regulation. This principle holds true with reference to the taxing powers of the States. A direct taxation of interstate or foreign commerce, that is of the goods carried as exports or imports, of the agencies and instrumentalities of such commerce as such, or of the act of carrying on, or the right to engage in or to carry on, interstate and foreign commerce, is always construed as a regulation of such commerce, and, as such, beyond the power of the States.

A State cannot even enforce the collection of a valid tax by an injunction restraining a person or corporation from doing interstate commercial business.48

46 202 U. S. 246; 26 Sup. Ct. Rep. 619; 50 L. ed. 1013. 47 Section 74.

48 Western Union Telegraph Co. v. Masaehusetts, 125 U. S. 530; 8 Sup. Ct. Rep. 961; 31 L. ed. 790.

In Osborne v. Mobile49 the court sustained a state tax which bore directly upon interstate commerce companies as such. The law in question in this case required every express or railroad company doing business in the city of Mobile and having a business extending beyond the limits of the State to pay a certain annual license fee. The court sustained the provision on the ground that there was no discrimination between the citizens of the State and the citizens of other States.

In Moran v. New Orleans50 this position was practically departed from, and in Leloup v. Mobile51 the doctrine absolutely and explicitly repudiated that any state tax however undiscriini-native, or whatever its other features, can be valid which imposes a burden upon persons or corporations engaged in interstate commerce, because of their being so engaged. The doctrine is in this case squarely laid down that no tax may be levied by a State which is imposed upon interstate commerce as such or operates as a direct burden thereupon. The court, after a review of authorities, say: " No State has the right to lay a tax on interstate commerce in any form, whether by way of duties laid on the transportation of the subjects of that commerce, or on the receipts derived from that transportation, or on the occupation or business of carrying it on, and the reason is that such taxation is a burden on that commerce, and demands a regulation of it, which belongs solely to Congress."

This doctrine, as thus stated, has now for many years been so well established that States no longer attempt to tax interstate commerce directly. Many state tax laws, however, though not expressly made applicable to interstate commerce transactions, have so substantially burdened commerce among the States as to raise the question whether they are not thus brought within the operation of the prohibition. It will be necessary, therefore, to consider the special cases in which the constitutionality of state tax laws have been tested by the Commerce Clause.

49 16 Wall. 479; 21 L. ed. 470

50 112 U. S. 69; 5 Sup. Ct. Rep. 38; 28 L. ed. 653.

51 127 U. S. 640; 8 Sup. Ct. Rep. 1383; 32 L. ed. 311.