The American Bar Association defined and adopted Model Standards of Conduct for Mediators in 2007. As described on the ABA's site:
"These standards are designed to serve as fundamental ethical guidelines for persons mediating in all practice contexts. They serve three goals: to guide the conduct of mediators, to inform the mediating parties, and to promote public confidence in mediation."
To download a .pdf copy of those Model Standards, use this link to the ABA's site: