S.D. Codified Laws § 49-16A-48
Whenever a resident of this state files a petition with the Department of Transportation, directed to the Interstate Commerce Commission of the United States, charging a railroad doing business in this state and engaged in interstate transportation of freight, with a violation of the Interstate Commerce Act of the United States, relating to abandonment, consolidation, merger, or inclusion, setting forth in the petition the facts constituting a violation, the department, if it deems the matter to be one of public interest, shall file the petition with the interstate commerce commission and appear in the matter in the place of the petitioner and prosecute the same at the expense of the state. Whenever the department determines that it is in the best interests of the State of South Dakota or its people, it may appear before the interstate commerce commission as a party in all proceedings relating to abandonment, consolidation, merger, or inclusion.
SDCL 49-16A-48