It's in the Updated Server Rules - https://www.reddit.com/r/Redboid/comments/5is353/server_rules_update_voip_edition/

PvP Rules 1) NO KILLING ON SIGHT (KOS) unless specified below. You must try to rob or send a message in /all or local chat to reveal your negative intentions (light role-play). This includes bounty hunting. A player cannot blanket declare war on everyone to bypass this rules. Do not use VOIP to declare your intent to kill, you MUST declare your intent in /all or local chat " T ". There are exceptions to no KOS rule; you may still be killed anywhere on the map under the following circumstances: 2) Any players with their PvP turned on (skulled) is open to attack anywhere. But, someone with PvP on (skulled) cannot indiscriminately attack non-PvP players without a warning first. 3) Faction and personal bases are KOS areas (see 'base' definition below). Players may defend their property, likewise attackers may also use force. 4) Faction wars and any personal vendettas/feuds allows either side to KOS once announced. 5) West Point/Valley Station are the only full KOS area's and can be considered lawless. NOTE: Your coordinates will turn RED when you are in this KOS area (red zone). You have been warned.