Ahh, well law.  Well (forgive the pun) this may be something that requires a declaratory judgment by a local court or something your state may actually regulate directly by statute.Let's see: It appears shared well regulations may be covered by subdivision rules within your county. Review the Water Rights section from the Office of the State Engineer. http://www.ose.state.nm.us/water_info_water_rights.html Also try the New Mexico Attorney General's office: http://www.nmag.gov/Since I don't know the county where these properties are, I cannot locate the specific regulation.  If none of these sources help, try www.attorneypages.com and look for an attorney.