I don't know what the solution should be, but it's going to be this:

    - Private militia getting paid per head taken off streets (check, already)
    
    - Said militia will start taking protection money
    
    - Everyone will realize ANYONE, citizen or not, can be taken repeatedly

These "joyrides" in jail for citizens will start as a couple of days of confinement as a harassment tactic. It will end in one of two ways - either Russia/Iraq/Syria style exile and torture camps. Or in Mexico cartel style, fully privatized and decentralized operations. The latter if the Federal Government keeps a light touch approach. (Which is very useful in itself, it can be used to foster a Wagner like extrajudicial force.)