Both parties have agreed to (go to) 'arbitration'.
a dispute settled by 'arbitration'
(..) - You treat us no better than dogs. - We shall supply you no more! - Enough! You have all called on Stormwind in the past either for troops or arbitration. If we do not unite to fight this enemy, we will perish. Stormwind needs soldiers, arms, horses... Ha! We have our own (..)2016 Warcraft