Minecraft wiki entry for Command_blocks_and_functions, associated text: By rigging a fast clock to a command block executing /teleport , they can force a player to stay at a certain place. If they do this it would be advisable to either turn off commands in their chat settings or do /gamerule commandBlockOutput false. Using the "Range" and "Minimum Range" parameters, they can have it teleport players back only when they're a certain distance away.