Miss. Code Ann. § 53-3-111

The portion of unit production allocated to a separately owned tract within the unit area shall be deemed, for all purposes, to have been actually produced from such tract, and operations with respect to any tract within the unit area shall be deemed for all purposes to be the conduct of operations for the production of oil or gas, or both, from each separately owned tract in the unit area. However, when an oil, gas and mineral lease contains land partially within and partially without said unit area, the unit agreement and production from the unit shall have no force and effect on lands lying outside of such unit area and failure of the lessee or lessees thereof to drill and develop such lands lying outside said unit area within one (1) year or during the term of the lease, whichever is a longer period of time, from the date of determination of the unit area by the state oil and gas board shall render such lease or leases on lands lying outside said unit area void and of no force and effect, unless otherwise held by production other than from unit production.