“That kind of lottery certainly does not confer legal binding to the order,” responded Rabbi Dayan, “since it is not similar to the division of Eretz Yisrael. Here the lottery does not even clarify the shares and certainly does not confirm ownership. Therefore, either party has the legal ability to retract [Pischei Teshuvah 173:2].
“I must add, though, that even where there is a legal possibility to retract it would usually be considered untrustworthy and morally reproachable.” (C.M. 204:7)