Is this covered by House Bill 5818?

The school I used to work at posted a piece of paper with pictures of former employees at the campus guard house that states the employees shown are no longer connected to the school and are therefore not allowed to enter the school premises unless they are accompanied by any of the school's current employees. This was done after an incident where 2 former employees went and gatecrashed a thesis defense. Do the former employees have the right to sue the school (claiming their rights as per house bill 5818)? What counter measures can the school do in this case? Can the school head be held accountable or the school as a corporate entity?Please help. Thank you.