Okay, I'm making good headway on the background for my fantasy novel about a witch who runs a potion shop, but I'm hitting a snag with one of the chapter plots. The basic idea of the chapter is, the emperor of the merpeople suddenly wants to institute a trade embargo between his empire and the surface, and the protagonist has to get involved and help the adventurer's guild resolve the issue. She is tasked at first with making a large quantity of Aqualung (potion that lets you breathe underwater) for their negotiation party, but insists on joining the party when she learns of the impending embargo because it would severely impact her business.

My quandary is, why would the emperor suddenly want to institute an embargo, and how can this dilemma be resolved? I've never tried to write anything political before, so any suggestions would be greatly appreciated!

EDIT: I found a solution! The emperor is instituting an embargo because he's tired of the land-dwellers dumping their waste into the ocean! Okay, this thread can be locked now. :P