N.M. Stat. § 22-4-18
Validation of previous annexation.
Every member of a local school board of a local school district which has been a
party to an annexation similar to that authorized in Section 1 [22-4-17 NMSA 1978] of
this act but occurring prior to the effective date of this act is determined to have been a
legally authorized governing authority and such annexation is validated as of the date of
the resolution adopting such action.