NEC code require for new installation and
modification of the circuit (if you modify it). It is legal to leave the existing as is if you didn't do any modification on the circuit.
Nothing can prevent the tenant to sue landlord for anythingfor your case: Fact, inspection tell you it does not meet the current code requirement. The current code requirement is for new installation and modification so you are not required by code to update them to meet current code. So, it is your call.