The Mansfeld Pact is an agreement formed a century before the Network Series takes placed between four of the five Networks. (Central, Eastern, Western, and Southern. The Northern Network had not been in communication with any other Network for centuries prior to that. Due to the difficult nature of the terrain, whether witches still live there isn't known.)
The Mansfeld Pact implicitly states each Network is to abstain from crossing into other Networks. No trade is allowed. Communication occurs between the leaders of the Networks (High Priests and/or High Priestess's) and Ambassadors as designated. If one Network breaks the Mansfeld. Each Network is required to set and maintain their border rules and provent their own witches from crossing borders. Breakage of the Mansfeld Pact with an act of war or aggression from one Network to another will remove the ability to do magic from those breaking the pact.