Regard for these important considerations of policy in the administration of federal equity jurisdiction is decisive here. If there was no warrant in state law for the Commission's assumption of authority, there is an end of the litigation; the constitutional issue does not arise. The law of Texas appears to furnish easy and ample means for determining the Commission's authority. . . .In the absence of any showing that these obvious methods for securing a definitive ruling in the state courts cannot be pursued with full protection of the constitutional claim, the district court should exercise its wise discretion by staying its hands. Compare Thompson v. Magnolia Co., 309 U.S. 478.
Railroad Comm'n of Texas v. Pullman Co., 312 US 496 (1941)