Many cities in and around Los Angeles, including the City of Los Angeles itself require certificates of registration (City of Los Angeles) or certificates of inspection (City of Pasadena) prior to leasing or renting out a unit, or lawfully collecting rents. California law suggests that a rental agreement for a rental unit which violates a local ordinance for example, would be void as against public policy and a landlord would not be entitled to past due rents. Whereas a landlord may be entitled to possession, the inability to collect rents based on a lack of certification, could prove fatal in an eviction trial premised on a failure to pay rent notice. Thus, landlords are best served ensuring the rental unit is properly certified and within the local city rules prior to demanding rents.