In Red Carpet-Barry & Associates v. Apex Associates, 130 Ariz. 302, 303, 635 P.2d 1224, 1225 (App. 1981) a real estate broker sued to recover a commission allegedly owed by sellers with whom he had a contract. The sellers moved to dismiss, arguing the written agreement was unenforceable because it lacked an expiration date. Id. The superior court agreed and dismissed the complaint. Id. On appeal, the Court affirmed. Id. The Court relied on then-existing rules of the real estate department, which we noted "have the force and effect of law," stating: The rules of the real estate department at the time this contract was made require that all real estate listings be in writing and that each listing agreement have a definite expiration date. . . . Since this rule is applicable to this contract, then the contract cannot be enforced since it is unlawful. Id. at 304, 635 P.2d at 1226.