Sovereign citizens are hilariously entertaining. I love it when they post videos of themselves in court and decide on their own that they "won" because the judge got pissed off and walked away after dismissing everyone.
You just have to meet them on their crazy level. Make a treaty with them that says something along the lines of "I corporation yourname hereby certify that my neighbor corporation theirname is a freeman of the land in-exchange that our territory boundaries are respected"