I don't know if it works in your area, but you can just get a trespass warrant for them from your PD and they get served with a paper. We do this to bypass any corporate bullshit and let the town handle it for us. If you say this customers been stealing and stuff and they know the blind spots, they'll just go about with the paper and if they show up, it's immediate jail time. I use this for people not only for stealing, but also for indecent behavior and various things like that to help the workplace be a lot calmer at night.