Boundary Enforcer
BattleArena comes pre-installed with a boundary enforcer module which ensures that players do not leave the bounds of an arena.
Configuring the Module
This module can be enabled by adding boundary-enforcer to the modules section of your Arena Configuration. No other configuration is required from this point, and once BattleArena has been reloaded with /battlearena reload, players will be unable to leave the arena boundaries configured in the Map Creation process.