RE: What would you do?
I would do like the property owner told you to do. Take them down. Instead of taking them home with me, ask the land owner to have the police come pick them up and then leave a note telling the person that if they want their stuff back to contact the local police. If the person does contact the police for their stuff then it is up to the land owner to decide whether they want to press charges against the person. That way your can wash your hands of the whole mess.