S.D. Codified Laws § 49-34A-42
Each electric utility has the exclusive right to provide electric service at retail at each and every location where it is serving a customer as of March 21, 1975, and to each and every present and future customer in its assigned service area. No electric utility shall render or extend electric service at retail within the assigned service area of another electric utility unless such other electric utility consents thereto in writing and the agreement is approved by the commission consistent with § 49-34A-55. However, any electric utility may extend its facilities through the assigned service area of another electric utility if the extension is necessary to facilitate the electric utility connecting its facilities or customers within its own assigned service area.
The commission shall have the jurisdiction to enforce the assigned service areas established by §§ 49-34A-42 to 49-34A-44, inclusive, and 49-34A-48 to 49-34A-59, inclusive.
SDCL 49-34A-42