What are they using the trail to access? Public land, or something else?
If the trail has been used for a long time, and you cut off access, they might challenge it in court.
They may (or may not) have a right to continued use of the trail, through a prescriptive easement through adverse possession.
If you Google "prescriptive easement", you will find lots of info.
How the judge would rule on this would depend on the details of the situation.
Last edited by troutbert; 11-25-2018 at 08:48 AM.