The U.S. Legal website defines 'Unlawful Entry' as an ". . . illegal entry upon lands or structures without force but by means of fraud or other willful wrong. It is closely related to housebreaking. But unlike housebreaking, the intent to commit an offense within the place entered is not needed for this offense. The basis of proof for this offense is that the entry was unlawful and that the conduct of the accused was contrary to good order and discipline. Burglary may be one of three types: forcible entry, attempted forcible entry, or unlawful entry. Unlawful entry refers to persons without the legal right to be on the property and who have gained entry even though force was not used."
The movie was made a year after the big box office hit Terminator 2 Judgement Day (1991) which also had a bad LAPD cop played by Robert Patrick but the twist was, he was a shape shifting terminator. Ray Liotta later worked with Robert Patrick on Cop Land in which they both were corrupt cops.
The name of the police force was the LAPD - the Los Angeles Police Department. Their motto and date of inception, as seen in the movie on a police vehicle, is "to serve and protect" being founded in 1781. In reality, the motto of the LAPD is "To Protect and to Serve" and was founded around 1853-1869.