Slitherine

Playing a MP game and I (Syracuse) am allied with my friend (Sparta). Thracia is a client state of Sparta, my ally, and it regularly raids my territory. I can't engage in diplomacy with them as they are a client state, and my friend playing Sparta tells me he has no options to control who they raid. How do I stop Thracia from raiding my land?

Offer gifts to Thracia until relations are over 25, or insult nations at war with them. Since they're a client state there won't be any possibility to negotiate a cooperation agreement, relations will keep deteriorating over time so you'll have to rinse & repeat after a while!