Facts
A. - By a written agreement dated March 29, 1983, the plaintiff I. undertook to pay the defendant F. 30,000 francs if [F.] mediated the purchase of a property in Zurich for him. On March 30, 1983, [F.] had a brokerage commission of 40,000 francs promised to him by the seller V. On April 5, 1983, the purchase contract between I. and V. was notarized. V. paid [F.] the 40,000 francs, while I. refused to pay the commission to F.
B. - [F.] sued I. for payment of the 30,000 francs and was granted provisional enforcement. I.'s action for denial was unsuccessful. I. has appealed the judgment of the High Court of the Canton of Lucerne, which upheld the first instance decision.
Considerations
1. The Federal Court holds that dual agency is permissible in this case, as the defendant [F.] limited himself to informing both parties of the possibility of concluding a contract, without further acting substantially for the buyer or seller. The agreement of March 29, 1983 did not contradict dual agency, and the plaintiff I., as an experienced real estate actor, had to expect that [F.] also wanted to act for the seller.
2. The broker has a duty to inform the client about his dual role only in cases where the permissibility of dual agency is doubtful.
3. a) The Federal Court finds that Art. 417 CO is mandatory law and a waiver of the reduction of a disproportionately high brokerage fee is not possible. The decisive factor is the total of all brokerage fees received by the dual broker, and not the individual amounts in relation to the purchase price.
b) The Federal Court considers the total commission of…