TN code annotated 39-11-614
in brief- you may use force to defend your property, but not deadly force with the following stipulations:
"...force is immediately necessary to prevent or terminate the other's trespass...or unlawful interference.."
or if you have been unlawfully dispossessed and want to immediately recover it.
TCA 39-11-615
"a person is justified in threatening or using force against another to protect real or personal property of a third person if, under the cirumstances of as the person reasonably believes them to be, the person would be justified under 39-11-614 in threatening or using force to protect the person's own real or personal property."
As I read these, in TN, a neighbor can use less than deadly force in the above scenario. Pepper spray, physical restraint, etc is fine. A firearm (or any other deadly force) is not.