' Even explicit charter provisions must yield to the paramount regulatory power of the Congress. State of New York v. United States, 257 U.S. 591, 601, 42 S.Ct. 239, 66 L.Ed. 385. Obligations assumed by the corporation under its charter of providing intrastate service are subordinate to the performance by it of its federal duty, also assumed, `efficiently to render transportation services in interstate commerce.' Colorado v. United States, supra, 271 U.S. at page 165, 46 S.Ct. at page 455, 70 L.Ed. 878. See Transit Commission v. United States, 284 U.S. 360, 367, 368, 52 S.Ct. 157, 76 L.Ed. 342; Transit Commission v. United States, 289 U.S. 121, 127, 53 S.Ct. 536, 77 L.Ed. 1075; State of Florida v. United States, 292 U.S. 1, 54 S.Ct. 603, 78 L.Ed. 1077. "* * * As thus construed, we find no ground for concluding that the approval of the provision in the lease was beyond the Commission's authority. There is no interference with the supervision of the state over the lessor in matters essentially of state concern, as distinguished from the operations which in their effect upon interstate commerce are of national concern."