The cop cannot PK you for any reason.
You are only ever subject to a pk when you initiate a violent confrontation against the officer. I.E. when you try to kill them.
As stated above by others there needs to be a real reason for players to fear police, or at the very least have consequences for choosing to interact with them in a certain way.
By choosing to remain peaceful you are subject to an arrest and can possibly be charged or imprisoned. However you may find yourself exonerated instead.
By choosing violence you decide to not want to interact with the police roleplay directly and escalate to murder (Given your kill reason is valid) but a possible consequence of failing this and being killed by an officer is your permanent death, similar to reality.
If this was not the case then why would you ever get arrested? If there was no serious consequence for killing a cop and dying you would much rather just die and respawn than suffer through an arrest & court proceedings, there's then no weight to your decisions and no risk to becoming violent. May as well be darkRP.
Similar to fear rp, it's enforced by the possibility of a PK, instead of having to micro manage players, as staff, and banning them. The player has their own choice and consequences.
If the cops are illegally entering a property then raise the issue in court.
If the cops are 'minging' about then call staff using '@'