As long as it's Taxed and Insured I'm sure it would be fine :-)
Another reason for not letting run an ic vehicle on forestry land would be the fire risk, may not be so risky this time of the year but a blanket ban is easier to enforce than seasonal allowances, consideration also has to be given to animal life that can be disrupted as unnatural noise can disturb many animals and prevent them from living and breeding in the area . I would go along with the others that have posted here and suggest that you try and discuss it politely with the guy (who is after all only doing his job to protect the environment), if you can convince him that you are responsible and concerned about safety, preservation and consideration of animal life he may be able to suggest a place that is suitable for you to run your car.