If he arrives to just non-bandits, then ask them what they are doing here. If they are here merely to aid Enderton in clearing the bridge of bandits, inform them that we will take it form there, then proceed to the garrison info for the bridge and enderton detailed in my orders. However, if they are trying to make the bridge owned by their house (as House Altright to the south may do judging from his diplomacy) kindly inform them that anybody and everybody can use both the bridge and the river that which passes under it, but that it actually belongs to the village of Enderton and by extension the House of Aarlehn. If they refuse to leave, attempt to use non-lethal force to force them to, but first make every possible effort to persuade them to leave first, including bringing the entire host to bear on them. If they resist, full assault.