促參案件因政策更迭致半途而廢者，雖不眾多，但並非罕見，我國現行促參法及行政程序法上對此問題，並未有完備周詳之規定，因此，本論文乃針對台北高行95年訴字第2710號判決及最高行98年判字第635號判決所涉及之板新汙水下道促參案，國內有關政策中止之首件判決，加以整理分析、剖析其在行政契約法上涉及之七大契約法理問題，包含議約完成後民間機構之法律地位，主辦機關之猶豫期間，促參投資契約之定性，國賠法第2條第2項之適用餘地，行政程序法第146條第2項，公法上不當得利及政策中止之定性問題，最後提出10點具體結論，作為未來立法修法及司法裁判之參考。

Promotion of Private Participation in Infrastructure Projects because the policy to gave up halfway, by no means rare, but ”Act for Promotion of Private Participation in Infrastructure Projects” and the ”Administrative Procedure Act” in our country to this question, which have some uncompleted stipulations, therefore, this paper focus on the 2710th decision in Taipei High Administrative Court of 95 years and the 635th decision Supreme Administrative Court of 98 years to involve the case about the sewer in Banciao, which analyzes it to involve seven big contract legal principles, includes the legal status of the folk organization after the contract completes, sponsor institution's hesitation period, Promotion of Private Participation in Infrastructure Project contract's character, State Compensation Law article 2 2nd item is suitable or not, Administrative Procedure Act article 146 2nd item, unjust enrichment shall apply mutatis mutandis in the public law, and the character of the discontinued policy, finally proposed 10 the conclusions, take the legislation and the judicial reference.