Legal Question in Legal Ethics in Oregon

Your relatives can sue the owners for breach of contract. The "damages" from the breach would be your relatives' lost profits (for some period of time) or the amount of money and effort they put into developing the location, including the cost of the liquor license.

A contract need not be written down; it can be oral. But oral contracts are hard to prove. How can your relatives prove that they had a contract with the owners? How can they prove what that contract called for? If they cannot prove these things, then they will lose the lawsuit.

Do your relatives have any letters or emails that indicate there was a contract or the terms of the agreement? Of course, your relatives can simply testify in court about the agreement and say that they certainly would not have gone to the expense of getting a liquor license and setting up the cart operation, if they did not have an agreement with the owners about the user of the area for a period of time. But the owners can, of course, deny this, and it will be up to a jury to decide who is telling the truth.