Tex. Loc. Gov't Code § 263.206

If the county does not own the fee simple title to land described by Section 263.203 or 263.204 and if the owner of the fee simple has executed an easement to the land for the purposes for which a conveyance is authorized under Section 263.203 or 263.204, the county judge, on order of the commissioners court, may join in and assent to the easement in the instrument granting the easement or in a separate instrument.