The elven ambassador keeps insisting I limit my wood harvesting to just over 100 trees per year. This is highly disruptive to my alcohol industry, as I require wood to make barrels for my brew. What happens if I disregard his requests and put my woodcutters in high gear?
Depends. Sometimes the elves will notice and take action, and other times they will ignore it.
If they do notice, it is also possible that the worst that can happen is that they leave as soon as they arrive. In a worst-case scenario, I think they can be provoked into outright fighting you. (Not sure if that counts as a war / siege)