truth with federation doesn't apply to all members

[Chrescerya]

I am frequently going to war with a federation next to me due to difference of opinion, their planets should be mine and they disagree Before due to size I had to rebuild each time after war, but currently been able to grow large and strong enough to overwhelm them. This is how I noticed that there is no truth with them, I can freely attack them again (button not disabled).

I think I am in a truth with 1 member (not even sure, need to check still) but at least with neighbour I declared war upon, I have no truth. (He is not the federation president).

 

[Aloriel]

If I am not mistaken, you do not have a truce with allies of your target. Therefore, you can attack the entire Federation again by attacking a second member of it. I disagree with this design choice (and most Paradox games do too), but it does seem to be the way it is for now.