My treaty prevents colonization in this system... |
... so claims the game. How come? I do not find any such treaty element. The only thing I have are a couple of non-aggression pacts (most only for neutral systems). Are they the cause?

My understanding is:
If you choose any treaty element except 3) Allow colonization of each others system, then whoever gets a system first, is the only treaty member allowed to colonize that system at all.
And, imho, this is one of the greatest additions to SE! No more can your "allies" who have a different breathable atmosphere come into your systems and setup their own mini empires while taking away your future planets.
I never select #3 unless its absolutly necessary...

Oops again!
This is why I shouldn't answer questions at work when a) Typing in a very minimized window and b) Don't have the game handy to reference.
Anyhow I should correct myself while I have the chance. The first option (in all neutral systems) will prevent you from colonizing any system outside of the ones you already have claimed.
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Me no like this treaty element
I think non-aggression and colonization are very different concepts that should be in seperate treaty elements.
I like not allowing combat in nuetral systems, but that doesn't mean I want to restrict colonization at all.
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With all these people, you would expect one of them to carry an iguana around...

Agression
As far as attack restrictions go, consider the difference between "we won't fire on your ships" and "oh, sure, place your ships inside my defence perimeter".
There are 10 types of people in the world:
Those that understand binary, and those that don't.




Non-Aggression = No Colonization
A Non-Aggression treaties either allows a) Party A to colonize only b) Party B to colonize or c) Neither can colonize claimed systems. A claim system is one where you already have a colony.
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