I do not think a player should be able to neg. a peace between an empire they are at with and another empire.

For example: I am fighting the Torians and I should not be able to convice them to make peace with the Yor when I am at war with them (the Torians).

IMHO it is too easy to keep the other empires in the game from snatching up easy systems/planets during the later stages of an AI empire's dismemberment by the player's empire.

By keeping everyone at peace with the player's enemies I have been able to gobble up several empires wholesale leaving nothing left for the other empires in the game. It is almost always worthwile to give them a tech or some cash while you snag the easy planets, esp. if you are at war with them and they will soon be no threat at all with that brand new tech they just traded for...

Just an observation.

GG