Minecraft wiki entry for Command_blocks_and_functions, associated text: Creating a "Creative Only" zone is possible through command blocks, but it is complex and more of a case-by-case basis. The basic idea would be to create a "fence" of command block affected zones so that, once a player flies in creative through it, they would be changed to survival or adventure mode. A "World Guard" zone would be a lot simpler, just have a command block do /gamemode adventure @a[x y z r m] and when people leave, just have a button to change them to survival.