The judgment below is reversed and the case is remanded to Seoul High Court.

The grounds of appeal are examined.

1. According to Article 78 of the former Act on Acquisition of and Compensation for Land, etc. for Public Works Projects (amended by Act No. 8665, Oct. 17, 2007; hereinafter “former Public Works Act”), with respect to the ground of appeal No. 1, a project operator shall either establish and implement relocation measures or pay resettlement funds as prescribed by the Presidential Decree for persons who are deprived of their base of livelihood due to the provision of residential buildings as a result of the implementation of public works (hereinafter “persons subject to relocation measures”), for the purpose of providing their residential buildings due to the implementation of public works (hereinafter “persons subject to relocation measures”), and the contents of relocation measures shall include basic living facilities according to the relevant regional conditions, such as roads, water supply and drainage facilities, and other public facilities, etc., in

(4) Therefore, if a special supply contract between a person subject to relocation measures and a project operator included the cost of basic living facilities as stipulated in Article 78(4) of the former Public Works Act in the sale price, the special supply contract includes the cost of basic living facilities in the sale price is null and void in violation of Article 78(4) of the former Public Works Act, which is a mandatory law.

(See Supreme Court en banc Decision 2007Da63089, 63096 Decided June 23, 2011). According to the reasoning of the lower judgment and the record, when the Defendant entered into a special supply contract with the person subject to the relocation measures of this case on a detached house, the Defendant calculated the supply price of the housing site by comparing the amount obtained by deducting the cost of installing basic living facilities according to the Defendant’s calculation method based on the cost of creating the housing site and the amount equivalent to 80% of the cost of creating the housing site. In light of the aforementioned legal principles, if the cost of installing basic living facilities is included in the supply price of the housing site, the Defendant’s unjust enrichment is deemed as unjust enrichment.