MR. JUSTICE BLACK delivered the opinion of the Court.
The California Motor Vehicle Fuel License Tax Act
Since § 10 of the California Act made the tax inapplicable "to any motor vehicle fuel sold to the government of the United States or any department thereof," it was necessary for the Supreme Court of California to determine whether the language of this exemption included sales to post exchanges. If the court's construction of § 10 of the Act had been based purely on local law, this construction would have been conclusive, and we should have to determine whether the statute so construed and applied is repugnant to the Federal Constitution. But in deciding that post exchanges were not "the government of the United States or any department thereof," the court did not rely upon the law of California. On the contrary, it relied upon its determination concerning the relationship between post exchanges and the Government of the United States, a relationship which is controlled by federal law. For post exchanges operate under regulations of the Secretary of War pursuant to federal authority. These regulations and the practices under them establish the relationship between the post exchange and the United States Government, and together with the relevant statutory and constitutional provisions from which they derive, afford the data upon which the legal status of the post exchange may be determined. It was upon a determination of a federal question, therefore, that the Supreme Court of California rested its conclusion that, by § 10, sales to post exchanges were not exempted from the tax. Since this determination of a federal question was by a state court, we are not bound by it. We proceed to consider whether it is correct.
On July 25, 1895, the Secretary of War, under authority of Congressional enactments
Congressional recognition that the activities of post exchanges are governmental has been frequent. Since 1903,
The commanding officer of an Army Post, subject to the regulations and the commands of his own superior officers, has complete authority to establish and maintain an exchange. He details a post exchange officer to manage its affairs. This officer and the commanding officers of the various company units make up a council which supervises exchange activities. None of these officers receives any compensation other than his regular salary. The object of the exchanges is to provide convenient and reliable sources where soldiers can obtain their ordinary needs at
From all of this, we conclude that post exchanges as now operated are arms of the Government deemed by it essential for the performance of governmental functions. They are integral parts of the War Department, share in fulfilling the duties entrusted to it, and partake of whatever immunities it may have under the Constitution and federal statutes. In concluding otherwise, the Supreme Court of California was in error.
Whether the California Supreme Court would have construed the Motor Vehicle Fuel License Act as applicable to post exchanges if it had decided the issue of legal status of post exchanges in accordance with this opinion, we have no way of knowing. Hence, a determination here of the constitutionality of such an application of the Act is not called for by the state of the record. Cf. Minnesota v. National Tea Co., 309 U.S. 551, 557. Accordingly, we reverse the judgment and remand the cause to the court below for further proceedings not inconsistent with this opinion.