We can do better than pinky swearing. Each lawyer gets mining fees when they enforce a contract fairly. "Fairly" is defined by consensus, where each lawyer is forced to predict the consensus before voting in a private ballot that is only revealed when the rewards are issued. Lawyers who predict the consensus get rewarded. If you start it off with people who are trying to be fair then predicting fairness will lead to the most reward, and it will keep going until the majority defects.
The collective is incentivized to continue being fair because if they weren't, nobody would use their coin, and the rewards issued to fair lawyers would be worthless.
The collective is incentivized to continue being fair because if they weren't, nobody would use their coin, and the rewards issued to fair lawyers would be worthless.