N.D. Cent. Code § 38-17-05

No coal lease executed after April 9, 1975, is valid for a primary term of more than twenty years, unless operations for mining are taking place on the leased land within the primary term, or the land is subject to a valid mining permit, and for so long thereafter as coal is regularly mined therefrom, or the land is subject to permit. This limitation does not prohibit agreements for extensions or renewals of the primary term.