So since people who are talking here are the ones who do not know how the system works in VC:MP, I'll elaborate from the beginning to the end, trying to be as accurate as I can be without my morning coffee.
ARPD Officers and VCPD Officers have one distinction; ARPD officers cannot be commanded around by high VCPD ranked officers, such as the chief. This may sound idiotic, but we will not force VCPD on those individuals who do not want to be a part of it, but do want to play the occasional cop. Also goodluck getting that new player who barely speaks english to listen to a command anyway

Now, if the ARPD Officer commits acts of corruption, both VCPD and FBI can discharge, suspect, jail, sue what have you. Corruption would be taking bribes for example, not killing other cops. If a VCPD Officer is caught breaking the law, they cannot be sued unless they are dishonorably discharged (
source)
Now for the copban part.
Copban is issued on cops as an
additive punishment on top of whatever they would have gotten anyway. Only exception to this is the "heliblade-a-smuggler" scenario which will always result in a copban. Admins can issue copbans on people along with a verbal warning, administrative warning, a kick or even a (temp)ban. Not a single cop in the server is safe from a copban, if they break the rules while on duty, they will receive the same punishment as the person
not on duty and get a copban on top in some scenarios.
Copban appears only to the admin and the player being copbanned because who got copbanned is irrelevant to other players. They do not need this information for anything but to bash on the copbanned target, which we do not want to see, regardless if they broke the rules or not.
Now why does VCPD not have copban? They were scripted to have /discharge to handle roleplay crimes and they are allowed to use it to minimize rulebreaks from cops
only if there is no admin online. Our administration team is more than active enough to handle basically everything, and the email "
[email protected]" is checked twice a day by yours truly. Not a single report is left un-handled for more than 48 hours.
Hopefully this'll paint a clearer picture for you guys.