Of course they can repossess the items: you have no  right to keep another's property without their consent and/or paying for it. So if the wheels are not paid for, they can take them back--the wheels belong to them, not you.They can file theft charges against your son for taking their wheels without (evidently) an intention to pay for them; and if you deliberately try to keep them (keep another's property) after knowing that you have no right to it (e.g. after the ask for them back), that trying to wrongfully keep another's property could potentially let them file theft charges against you, too.They could also sue your son-in-law for breach of contract, for all the money due under the agreement.You could sue your son-in-law for any amounts this wrongful act ends up costing you, and/or for the value of the tires and wheels he destroyed in the first  place.