/safezone create <X start> <Z start> <X end> <Z end>
No need to check if new "safe zone" overlaps old ones because this would not cause problems.
<ID> <X start> <Z start> to <X end> <Z end>
1 253 150 to 263 160
2 1500 150 to 1600 250
/safezone delete <ID #>
Another example of use would be a shop area. Players could safely use shop signs without being killed by PvP.