Did Jorb forget to mention that? It's quite a core part of it all. :)
Authority objects have the following restrictions on their location of erection:
* They must be built either within the influence of an existing authority object, or so that the new object's influence would include an existing object.
* They cannot be build so that they would influence the authority objects of other villages.
* They cannot be built too close to other authority objects.
That last point is a bit underrepresented in the game UI right now. Each authority object has a radius within which no other authority objects may be built (which is, obviously, smaller than its radius of influence), but that radius is not actually indicated anywhere; you'll just get an error message if you try to build them too close to each other.
The implications of these rules should be quite obvious.