You may have seen a few of these around already: border stones.
they have been placed at the mud equivalents of the closest matching bookish borders.
While we aim to let players run things as much as is possible, history has shown us that unless controlled, players would claim every inch of land they possibly can, whether they have bookish reason to or not. This, however, brings with it problems with regards to hunting wanteds, contesting jurisdictions and generally every patch of land claimed. We feel this also puts a damper on more illicit activities.
Because of this, we have placed border stones in order to fence off jurisdictions and create swathes of unclaimed lands. After all, just because you post on ToL that you claim it, doesn't mean you actually own it.