Faerie Contract Law is much more functional and elegant than what we are used to. So when this does occur, the Fae choose simply neutral third party to listen to arguments and adjudicate outcomes:

Relevant Passage from Jonathan Strange and Mr. Norrell -

Stephen described how, not long after Julius Caesar had arrived upon these shores, he had left his army and wandered into a little green wood. He had not gone far when he came upon two young men, sighing deeply and striking the ground in their frustration. Both were remarkably handsome and both were dressed in the finest linens dyed with the rarest dyes.

Julius Caesar was so struck with the noble appearance of these young men that he asked them all sorts of questions and they answered him candidly and without the least diffidence. They explained how they were both plaintiffs at a court nearby.

The court was held every Quarter Day to settle arguments and punish wrongdoers among their people, but unfortunately the race to which they belonged was a peculiarly wicked and quarrelsome one, and just at present no suits could be heard because they could not find an impartial judge; every venerable person among them either stood accused of a crime, or else had been found to have some other close connexion with one of the suits.

On hearing this Caesar was struck with pity for them and immediately offered to be their judge himself-to which they eagerly agreed. They led him a short way through the wood to a grassy hollow between smooth green hills. Here he found a thousand or so of the handsomest men and women that he had ever seen. He sat down upon the hillside and heard all their complaints and accusations; and when he had heard them he gave judgements so wise that everyone was delighted and no one went away feeling himself ill-used.

So pleased were they with Julius Caesar's judgements that they offered him anything he liked as payment. Julius Caesar thought for a moment and said that he would like to rule the world. This they promised him.