How do you make peace with the Pirates in 117?

I'm far enough on an easy play to have built the Coliseum. Thirty hours in and several cease-fire pacts with the Roman pirates. I still can't make peace with him. I'm at a 70 rating with the Empress.

Is there a research that allows peace treaties with the pirates? Or do I need to get max rep with the Empress to unlock the option?

Or is it simply just not possible right now?