I really don't see the issue. If Diktat can do it without punishment then maybe it's because they have enough influence with other factions that they can pull it off. Maybe there are backdoor deals to stop new competitors from popping up. Maybe they are threatening others with military action. Maybe losing the access to the premier fuel source of the sector would be too much of a collateral. Etc, etc,
I think ideally some factions should always be annoyed, triggering sector wars, but other than that there is really no reason to hold the AI factions to the same standards as the player's, this isn't Stellaris. In fact, they don't even expand. The reason I think this is preferable is because you can make factions more unique if they can do things that the player can't do (at least not easily), and you'd have to consider the different points of each. "Oh, gotta be careful about competing with this faction, can't simply just make some fuel and get a quick buck without some severe consequences."