Regarding this composition, in 1966, the Committee of Commerce and Industry of the House of Councilors, a member (at that time) Kazuhiro SUZUKI questioned its validity, and the representatives of the Ministry of Agriculture and Forestry and of the Ministry of International Trade and Industry answered that they did not think the final composition had been valid nor was valid, since it was doubtful that the chairperson of the water supply union had had the authority to make such a composition with a company and after the composition the mining pollution had been ruining them.
この契約書に関しては、1966年、参議院商工委員会で鈴木一弘委員（当時）が有効性があるのかと問いただしたところ、農林省、通産省の担当者は、それぞれ、契約書に署名した水利組合理事長に独断でそのような契約を結ぶ権限があったか疑わしく、また、契約後も鉱毒被害が発生していることから、永久示談の成立には否定的な答弁を行っている。