S.D. Codified Laws § 49-31-4
Any charge established for the provision of telecommunications services shall be fair and reasonable. The commission shall determine and approve individual rates to be charged by any telecommunications company for a noncompetitive service pursuant to § 49-31-1.4, if applicable, and pursuant to §§ 49-31-12, 49-31-12.2 and 49-31-12.4. Except as provided in § 49-31-4.1, the commission shall utilize rate of return regulation when determining the charge for a noncompetitive service.
The commission shall determine and approve individual prices to be charged by a telecommunications company for any emerging competitive service pursuant to §§ 49-31-1.4, 49-31-12, 49-31-12.2 and 49-31-12.5. However, there is no rate of return regulation of emerging competitive services and no rate of return or price regulation of fully competitive services.
The commission shall separate, assign and distribute a telecommunications company's revenues, investments, and expenses among all services offered. The commission shall, by rules promulgated pursuant to chapter 1-26, prescribe the methodologies by which a telecommunications company shall segregate its revenues, investments and expenses. The methodologies prescribed by the rules shall be in accord with federal and state law. No telecommunications company may use the revenues from emerging competitive services to subsidize fully competitive services or revenues from noncompetitive services to subsidize emerging competitive services or fully competitive services. Expenses and investment of fully competitive services may not be attributed to emerging competitive services or noncompetitive services and the expenses and investment of emerging competitive services may not be attributed to noncompetitive services.
Rates being charged by a telecommunications company on July 1, 1988, shall be deemed to be the fair, reasonable, and effective rates until changed or altered pursuant to this chapter.
SDCL 49-31-4