Cop Tells My Technician No Oil Changes On Private Property

I'm a fleet Manager in Florida for a delivery company that leases a parking area from another local business. We've been parking here for years and have technicians that work around the clock to maintain our fleet including oil changes that are done in our parking lot. Yesterday a cop came up to my tech late at night to tell him he's there to make sure he's not doing any oil changes and told him oil changes are not allowed here. Apparently this cop hangs out in our parking lot almost every night. No oil changes were on the schedule that night, but the cop proceeded to sit in his car for hours watching him. We park at a giant private parking lot, which we lease a small section of it to park our fleet. If I were the tech I would of told the cop to get off our property. I wouldn't think the cop would have any authority to tell us we cant do oil changes on private property? Is that accurate? I want to nip this in the bud before our repair company starts to refuse doing oil changes. It would be a major PITA if we have to start taking trucks offsite one at a time to have PMs done.