Illegal Synthetic Drug Safety Act of 2017 This bill amends the Controlled Substances Act to modify the treatment of controlled substance analogues (i.e., substances that have substantially similar chemical structures and pharmacological effects to schedule I controlled substances). Under current law, a controlled substance analogue that is intended for human consumption is treated as a schedule I controlled substance. This bill replaces the "intended for human consumption" qualifier with a "not a chemical substance subject to the Toxic Substances Control Act" qualifier. Specifically, a controlled substance analogue that is not a chemical substance under the Toxic Substances Control Act is treated as a schedule I controlled substance.