I think the spirit of contract is a reasonable gambling policy we all should comply with.

There is no completely fair rule or regulation.

Things are changing and altering and the same in how  people thinking. To avoid disputes which may happen afterward, we all need to reach an agreement in advance and then comply with it. Somehow the agreement is just like the the counter of gambling  because we can not predict or forecast all the possible situation and the coincidence which we are not expecting. But we need a rule to play with it and continue the play.