In Ambassador, Inc. v. United States, 325 U.S. 317, 65 S.Ct. 1151, 89 L.Ed. 1637 (1945), the Supreme Court considered the validity of a preliminary injunction issued against hotels in violation of a tariff regulation imposed by the telephone company. The tariff regulation had been filed in compliance with an FCC rulemaking order and had not been specifically upheld by the FCC as reasonable. The Supreme Court, in sustaining the injunction, upheld the district court's determination that the defendant hotels were in violation of the regulation and found that the suit to enjoin the violation was authorized under "47 U.S.C. Sec. 401." Although the Court failed to specify the subsection of Sec. 401 to which it was referring, it is clear that the suit had to have been brought under Sec. 401(b) since Sec. 401(a) only authorizes a district court to enjoin violations of the Act itself. If Sec. 401(b) is available to enforce tariff regulations filed pursuant to agency rulemaking, the section should surely be available also to enforce rules and regulations of the agency itself.