Stop the Importation and Trafficking of Synthetic Analogues Act of 2017 or the SITSA Act This bill amends the Controlled Substances Act to establish a new, sixth schedule of controlled substances—schedule A. A drug or substance in schedule A has a chemical structure that is similar to, and an effect on the body that is similar to or greater than, a controlled substance in schedule I, II, III, IV, or V. The bill adds 13 synthetic fentanyl-related substances to schedule A. It also authorizes, and establishes procedures for, the Drug Enforcement Administration (DEA) to temporarily and permanently place a drug or substance in schedule A. The bill establishes criminal penalties for an individual who imports, exports, manufactures, distributes, or possesses with intent to distribute a schedule A substance. However, it explicitly prohibits criminal and civil penalties solely for possession of a schedule A controlled substance. The bill makes it unlawful to import, export, manufacture, distribute, dispense, or possess with intent to manufacture, distribute, or dispense, a schedule A substance that is not clearly labeled. Finally, it establishes new, separate DEA registration requirements for manufacturers, distributors, and importers and exporters of schedule A substances.