All signs erected by the department, after July 1, 1967, which give notice of the prohibition against the cultivation of the right of way, must be located as near as possible to right-of-way posts, or natural obstructions. All existing signs of such nature must be relocated according to the provisions contained in this section, and when requested by the landowner and a more suitable site can be agreed upon by the landowner and the department.
N.D.C.C. § 24-01-08.1