If you have a good relationship with the landowner, I would go to her and have a thorough conversation with her explaining the situation. I think that it will be quickly resolved with the "problem hunters" being forced off the property. If she told you to hunt the property as if it was yours maybe she will put it in writing. Offer to lease the property if necessary including the offer to include hunters insurance with your party as the only hunters covered. Then you can have the CO remove them as tresspassers. Don't give up your hard earned place to hunt because of the action of a couple of punks.