First off boot him now rather than later. It will give him time to find new area and get over the disappointment of being booted yet a 3rd time. If you wait he may just show up to ruin the day. I would say the guy that invited him is the guy that should kick him! I am sure the majority wants him gone so if you desire a letter with all the signatures that would work to be presented to him when approached...but don't mail it to him. Face to face and explain your reasons and safety concerns...maybe he'll get the picture. If your buddy won't do it, then you or someone else do it.

To me safety is number #1, but having a good time is important...guys shooting grouse or trees isn't going to help the good time, safety is being thrown out the window and it will effect the success of the group. Kick this dead beat to the curb NOW!