70-20-403. Grant by person with power to revoke -- power executed. (1) When a power to revoke or modify an instrument affecting the title to or enjoyment of an estate in real property is reserved to the grantor or given to any other person, a subsequent grant of or charge upon the estate by the person having the power of revocation in favor of a purchaser or encumbrancer for value operates as a revocation of the original instrument, to the extent of the power, in favor of the purchaser or encumbrancer.

(2) When a person having a power of revocation within the provisions of subsection (1) is not entitled to execute it until after the time at which the person makes the grant or charge as described in that subsection, the power is considered to be executed as soon as the person is entitled to execute it.