S.D. Codified Laws § 28-18-20
If any provision of §§ 28-18-7 to 28-18-19, inclusive, or any resolution or resolutions authorizing the issuance of bonds pursuant to said sections, or the application thereof to any person or circumstances, shall be held invalid in any legal proceedings, such invalidity shall not affect other provisions or applications of said sections or of such resolutions which can be given effect without the invalid provision or application, and shall not affect the validity of such bonds as special and limited obligations of the municipality issuing the same, and to this end all such resolutions shall be subject to all of the provisions and limitations of said sections, and the provisions and applications of said sections are declared to be severable.
SDCL 28-18-20