Is this a bug or a feature: due to a random event, the Drath Legion (my ally) went to war with the Terrans (also my ally). I took this opportunity to declare war on the Terrans myself (so much for my Good alignment, I guess

). Now, this turn, I see that diplomacy icon 'The Terrans have signed a peace agreement with the Drath Legion', and also another one saying 'The Terrans have signed a peace agreement with us'.
I was shocked. Someone has been agreeing to peace treaties on my behalf, behind my back! I never got any diplomacy screen from the Terrans whether maybe I would like to sign a peace treaty with them! Did that happen because they signed a peace treaty with one of my allies?