(b) Whether Article 536 of the Civil Act shall apply mutatis mutandis to cases where it is necessary to return one another's acquisition of bilateral contracts.

B. The purport of Article 536 of the Civil Act, which provides for the right to defense of simultaneous performance, is due to the merger between the concept of fairness and the principle of good faith. Considering that Article 536 of the Civil Act is applied mutatis mutandis to the duty to restore each party in the case of rescission of a contract pursuant to Article 549 of the Civil Act, it is reasonable to apply Article 536 of the Civil Act by deeming that there exists a simultaneous performance relationship even in the

The appeals by Defendants 1 and 2 are dismissed, and the costs of appeal are assessed against the Defendants.

(A) On the first ground for appeal

In its reasoning, the court below held that, among the apartment units of 660 households that the Plaintiff’s association established to implement a housing improvement redevelopment project on the 229 parcel of land located in Gwanak-gu in Seoul Special Metropolitan City, the apartment units of 13 households, including the third apartment units listed in the attached Table of the judgment of the court below (hereinafter “the apartment units of this case”) have been designated as a withholding construction facility pursuant to Article 43 of the Urban Redevelopment Act, etc., but the non-party 1 and the non-party 2 who are the directors of the Plaintiff’s association agreed to dispose of the apartment units of this case at their own discretion as if they were legitimately sold the apartment units of this case and prepared and delivered the apartment unit sale contract between the non-party 3 (the record shows that the non-party 3 had already died) and the Plaintiff’s association, and thereby, the above non-party 1 and the non-party 2 did not have the status to conclude the sales contract of this case as to the apartment units of this case.

However, according to the facts established by the court below, the above non-party 1 is a full-time director who has overall control over the whole business of the plaintiff's association, such as apartment sale, and the above non-party 2 is a full-time director who has overall control over the whole business of the association, such as supervision over the construction site of the new apartment. Meanwhile, according to the records, the head of the plaintiff's association is non-standing and it can be seen that the above non-party 1 et al. was in a position to enter into a sales contract, etc. for the plaintiff's association. Thus, the above non-party 1 et al. was in a position to enter into a sales contract, etc. for the plaintiff's association. Thus, the court below erred in holding that the above non-party 1 et al. did not enter into a sales contract at all, but

However, as examined below, as long as the validity of the above sales contract cannot be recognized because there was no resolution of the general meeting of partners with regard to the disposal of the apartment of this case, the above error of the court below shall not affect the conclusion of the judgment, and as such, the argument that the court below erred in the misapprehension of legal principles as to the lack of reason, the contradiction of reason, and the burden of proof shall return to the court below's decision without merit.

(B) On the second and third grounds for appeal

According to Articles 23(3)8 and 43 of the Urban Redevelopment Act, when a redevelopment cooperative disposes of withheld construction facilities, etc., it shall undergo a resolution at the general meeting of the association members (the articles of association of the Plaintiff cooperative or the Seoul Special Metropolitan City’s guidelines for the business of housing improvement redevelopment project). Thus, the disposition of withheld construction facilities conducted by the redevelopment cooperative without a resolution at the general meeting of the association members is invalid. However, the above non-party 1, etc. did not undergo a resolution at the general meeting of the association members when they enter into the sales contract with the above non-party 3 regarding the apartment of this case, which is the withheld construction facilities. Thus, the above sales contract is null

In addition, even if there is room for analogical application of the provision on acting representation, such as the theory of novels, the above provision on acting representation, as determined by the court below, in light of the fact that the above non-party 3, who worked as the director of ○○○○○○○○○○○○○○, had already been completed the sale of the above redevelopment apartment and had been sold the apartment of this case in the form of general sale with the introduction of directors of the above company who had worked at the above site after the completion of the general sale of the above redevelopment apartment, and solicited the above non-party 1, etc. to the above non-party 1, etc., it is difficult to see that the above non-party 3 did not know that there

The judgment of the court below which seems to be the same purport is just, and there is no error of law by misunderstanding the legal principles as to the validity of acts violating the regulations such as the Urban Redevelopment Act or the limitation of power of representation under the laws and regulations, and therefore the argument

(C) On the fourth ground of appeal

According to the reasoning of the judgment below, the court below rejected the plaintiff's assertion that the above defendants possessed the apartment of this case with the above non-party 3's consent, and that the sale of the apartment of this case was committed a tort against the non-party 1, etc., who was a director of the plaintiff's association, and therefore, the plaintiff's association has a duty to compensate the above non-party 3 for a considerable amount of the market price of the apartment of this case, which is the above non-party 3 or the above defendants' liability for damages against the above non-party 1, etc., even if the plaintiff's association's liability for damages against the above non-party 1, etc. is recognized, it cannot be deemed that the

However, according to the records, the above defendants' assertion of simultaneous performance of the obligation of compensation for damages equivalent to the market price is asserted to cope with the claims that the above non-party 1 et al. were not in a position to enter into the sale contract at all, and that there was no resolution of the members' general meeting. Thus, the market price of the apartment of this case at the time of sale can be known that the above non-party 3 reached the sale price paid by the above non-party 3. Thus, it is reasonable to view that the above defendants' assertion contained the purport of claiming simultaneous performance with the obligation of return for the sale price if the above contract cannot be asserted for the validity of the sale contract on the ground that the resolution of the general meeting of the members

Meanwhile, the purport of Article 536 of the Civil Act, which provides the right of defense for simultaneous performance, is due to the merger between the concept of fairness and the principle of good faith. When considering that Article 536 of the Civil Act is applied mutatis mutandis to the duty to restore each party in the event of rescission of a contract pursuant to Article 549 of the Civil Act, it shall be reasonable to apply Article 536 of the Civil Act to the case where the bilateral contract becomes null and void and each party shall return the acquisition of each other (see, e.g., Supreme Court Decision 93Da1622, Sept. 10, 1993). If the above contract becomes null and void for the reasons as seen above, the plaintiff's duty to return the purchase price of the apartment of this case and the above duty to explain of the non-party 3 is in the simultaneous performance relationship. Thus, the above defendants have the right to possess the apartment of this case until they receive the above purchase price from the plaintiff by exercising their right of defense for simultaneous performance, and therefore, if they occupy the apartment of this case with the above non-party 3's right to use.

Nevertheless, the court below's rejection of the above defendants' assertion on the grounds stated in its reasoning is erroneous in the misunderstanding of legal principles as to simultaneous performance, and it is clear that this affected the judgment. Therefore, the ground for appeal pointing this out is justified.

2. The appeal by the defendant 1 and the defendant 2 is examined.

The above Defendants did not submit the appellate brief and did not state any grounds of appeal in the petition of appeal, and thus, the appeal by the above Defendants cannot be dismissed.

3. Therefore, the part of the judgment of the court below regarding Defendants 3 and 4 is reversed, and that part of the case is remanded to the court below. The appeal by Defendants 1 and 2 is dismissed, respectively. The costs of appeal by this part are assessed against the above Defendants. It is so decided as per Disposition by the assent of all participating Justices on the bench.

Justices Lee Yong-hun (Presiding Justice)