We have trails here specifically closed to Mtn Bikers. Hiking and 4 Wheelers (Hunters) allowed. TWRA is a gov't body that enforces this. If they catch you there you get a warning. The second time they fine you $169. The Third Time they confiscate your bike and you get 7 days in the local prison. Just to answer what is the worst that could happen.

I never ride forbidden trails but only partly out of a sense of obligation. ANd also somewhat out of fear of the consequensces. Always be aware getting the trails open for others by respecting the restrictions and working the system is always more appropriate and that there may be someone that is working on that for you that you are hurting their cause with your reckless abandon.

Just thoughts. Ride on!