can do src mod, but can do function with sql too, that when a player warps to pvp map, change the group id of the player to a group that has no command privilege, then when player moves out of the map, return him to the group with ur typical available @cmds.
about the src, find in src\map\atcommand.c the functions of load, warp, go and die and put there a checker if player state is on pvp, when they use the command, return -1;