High quality reprint of this recently declassified 1977 study. This report is the fourth in a series of CHECO reports on the ROE, summarizing significant events and changes which occurred between October 1972 and August 1973. Throughout this period, the operating authorities formulated by the JCS were in most cases directly related to the peace negotiations conducted in Paris between the United States and the Democratic Republic of Vietnam (DRV). Consequently, this report accounts for changes in the ROE, chronologically, as they applied to the different areas of SEA: The Republic of Vietnam (RVN), North Vietnam (NVN), Laos, and Cambodia. This presentation not only provides the reader with significant changes in the ROE between October 1972 and August 1973, but also portrays the close relationship between national policy and the conduct of air operations in SEA. The intensity of bombing, the number of sorties authorized, and the territorial restrictions were constantly changed, particularly through January 1973. Specifically, they followed the negotiating trends and the sincerity, or the lack of it, with which the North Vietnamese approached peace negotiations. These negotiations culminated in the signing of the "Agreement on Ending the War and Restoring Peace in Vietnam" on 27 January 1973 in Paris. Because these changes would be less significant to the reader without some prior knowledge of the ROE, this chapter provides a brief summary of the ROE as they stood in September 1972.