A more thorough explanation:

Nullum arbitrium

Nullum arbitrium is a legal term that means "no decision." It was used in cases where someone was trying to enforce an arbitration bond, but the other party denied that there was an arbitration award.

For example, let's say that two people had a disagreement and agreed to have an arbitrator decide the outcome. They signed a contract that said they would abide by the arbitrator's decision. However, when the arbitrator made a decision, one of the parties refused to accept it. In this case, the other party could use the plea of nullum arbitrium to argue that there was, in fact, an arbitration award and that the other party was not abiding by the contract.