On March 18, 1938, the FCC (D) undertook a comprehensive investigation to determine whether special regulations applicable to radio stations engaged in chain broadcasting were required in the 'public interest, convenience, or necessity.' A committee of three Commissioners was designated to hold hearings and make recommendations to the full Commission. This committee held public hearings for 73 days over a period of six months, from November 14, 1938, to May 19, 1939. Almost 100 witnesses were heard by the committee, 45 of whom were called by the national networks. The evidence covers 27 volumes, including over 8,000 pages of transcript and more than 700 exhibits. The testimony of the witnesses called by the national networks fills more than 6,000 pages, the equivalent of 46 hearing days. The committee submitted a report to the Commission and briefs on behalf of the networks, and other interested parties were filed before the full Commission. The Commission issued proposed regulations which the parties were requested to consider in the oral arguments held on December 2 and 3, 1940. Supplementary briefs were filed discussing at length the questions raised by the committee report and the proposed regulations. On May 2, 1941, the Commission issued its Report on Chain Broadcasting, setting forth its findings and conclusions upon the matters explored in the investigation, together with an order adopting the Regulations here assailed. Since October 30, 1941, when the present suits were filed, the enforcement of the Regulations has been stayed either voluntarily by the Commission or by order of court. Ps, in essence, wanted an injunction against enforcement of the regulations as an unauthorized and unconstitutional exercise of administrative power.