The arbitrators were a group of people in Carvahall charged with resolving certain disputes of a legal nature. The arbitrators were mentioned in regard to a dispute between Thane and Albriech in Eldest. After the two had a row, Roran stated that an assembly could be called and arbitrators would determine whether or not compensation was due to anyone.
As no names were mentioned, it was possible that there was no specifically assigned group of arbitrators and that they were instead chosen on a case-by-case basis. They were never mentioned again in the series, as the people of Carvahall soon fled their village and joined the Varden.
Those that were unable or unwilling to settle their problems via arbitration could choose to escalate a matter by declaring a blood feud.