Model U.N. Charter is a book with the rules of the Model U.N. Club.
Lisa took the book at the weekend U.N. Later on the island, when Bart, Milhouse and she were hunted by other children, the three hid in the cave. However, the children found them and wanted to kill them. Lisa tried to stop them saying that they were infringing the Model U.N. Charter. The children suddenly stopped. Lisa had thought that they did because of the Charter, until she noticed a wild boar behind her. The scared children started running out of the cave and left the Charter there.