Why? In most cases the registered disabled at a site register and have access granted.
Prevention as you say is open to abuse and while I would not give them a good kicking, but chain them to a wheelchair for a month, both is wrong. And lets face it the person who uses a space is unlikely to be a pleasant individual. I remember warning someone off parking and was given some foul mouthed abuse. I warned them, and when they returned they had two two meter high paladins blocking them. Padlocked. I said its refuse day. When I got an apology I unlocked them.
Securing a space means that it is guaranteed and works in the majority of situations.
Based on the information posted, I offer my thoughts.Any action you then take is your liability. While commending individual effort, there is no substitute for a thorough review of documents and facts by paid for professional advisers.