I don't claim to be an expert on any of this, but this is a common thing for parks to do when they have problems like this.
My background with theme parks goes back to Six Flags Great Adventure, the first park in the world to install metal detectors way back in 1987. The park had problems with guns, drugs, knives, gang fights, and robberies.
Years later when it came to Fright Fest they were having similar issues and instituted the same "no re-entry" policy just for those specific times when there was a potential threat to peace and security in the park. I don't know the details of why, but I know they determined that having people leaving the park and returning was contributing to the problem. Whether it's people drinking, getting high, bringing in contraband, or whatever it apparently helps the situation.
This is not a permanent policy change, this is a "we are doing this today for safety" temporary thing.