Legal Question in Business Law in California

I'd say that keys for "tenants" such as booth renters in salons is a matter of private agreement and contract, and not regulated or governed by any written law or unwritten policies or court decisions. If you have an agreement in place for your rental, does it mention keys or access? If it did, the agreement terms would govern; if not formal agreement or if it is silent on this point, the owner probably can have it his way, assuming you at least have reasonable access while the salon is open.