MR. JUSTICE FRANKFURTER delivered the opinion of the Court.
This is a suit brought in a United States district court to enjoin the enforcement of a State tax and for a declaratory judgment.
The Connecticut Corporation Business Tax Act of 1935, as amended, imposed on every corporation, not otherwise specially taxed, carrying on or having the right to carry
The District Court construed the statute to be "a tax upon the exercise of a franchise to carry on intrastate commerce in the state" and therefore not applicable to petitioner. 47 F.Supp. 671, 675. On appeal the Circuit Court of Appeals for the Second Circuit construed the statute to reach all corporations having activity in Connecticut, whether doing or authorized to do intrastate business or, like the petitioner, engaged exclusively in interstate commerce. It further decided all contentions under the Connecticut
Once doubts purely local to the Constitution and laws of Connecticut are resolved against the petitioner there are at stake in this case questions of moment touching the taxing powers of the States and their relation to the overriding national interests embodied in the Commerce Clause. This is so whether the issue be as broad and as bare as the District Court and Judge Learned Hand formulated it, or whether the Connecticut statute carries a more restricted meaning. If Connecticut in fact sought to tax the right to engage in interstate commerce, a long course of constitutional history and "an unbroken line of decisions" would indeed be brought into question. But even if Connecticut seeks merely to levy a tax on the net income of this interstate trucking business for activities attributed to Connecticut, questions under the Commerce Clause still remain if only because of what the court below called "ingenious provisions as to allocation of net income in the case of business carried on partly without the state." 139 F.2d 809, 812.
Answers to all these questions must precede consideration of the Commerce Clause. To none have we an authoritative answer. Nor can we give one. Only the Supreme Court of Errors of Connecticut can give such an answer. But this tax has not yet been considered or construed by the Connecticut courts. We have no authoritative pronouncements to guide us as to its nature and application. That the answers are not obvious is evidenced by the different conclusions as to the scope of the statute reached by the two lower courts. The Connecticut Supreme Court may disagree with the District Court and agree with the Circuit Court of Appeals as to the applicability of the statute. But this is an assumption and at best "a forecast rather than a determination." Railroad Commission v. Pullman Co., 312 U.S. 496, 499. Equally are we without power to pass definitively on the other claims urged under Articles I and II of the Connecticut Constitution.
If there is one doctrine more deeply rooted than any other in the process of constitutional adjudication, it is that we ought not to pass on questions of constitutionality — here the distribution of the taxing power as between the State and the Nation — unless such adjudication is unavoidable. And so, as questions of federal constitutional power have become more and more intertwined with preliminary doubts about local law, we have insisted that federal courts do not decide questions of constitutionality on the basis of preliminary guesses regarding local law. Railroad Commission v. Pullman Co., supra; Chicago v. Fieldcrest Dairies, 316 U.S. 168; In re Central R. Co. of New Jersey, 136 F.2d 633. See also Burford v. Sun Oil Co., 319 U.S. 315; Meredith v. Winter Haven, 320 U.S. 228, 235; Green v. Phillips Petroleum Co., 119 F.2d 466; Findley v. Odland, 127 F.2d 948; United States v. 150.29 Acres of Land, 135 F.2d 878. Avoidance of such guesswork, by holding the litigation in the federal courts until definite determinations on local law are made by the state courts, merely heeds this time-honored canon of constitutional adjudication.
We think this procedure should be followed in this case. The District Court had jurisdiction to entertain this bill and to give whatever relief is appropriate despite the Johnson Act
We therefore vacate the judgment of the Circuit Court of Appeals and remand the cause to the District Court with directions to retain the bill pending the determination of proceedings to be brought with reasonable promptitude in the State court in conformity with this opinion.
MR. JUSTICE DOUGLAS concurs in the result.
MR. JUSTICE BLACK dissents.