Temporary Scheduling Authority of the US Attorney General and the DEA
"Because policymakers were concerned about the effects of pharmaceutically created and other modified drugs, Congress gave the Attorney General the authority to temporarily place a substance onto Schedule I of the CSA to 'avoid imminent hazards to public safety.13 When determining whether there is an imminent hazard, the Attorney General (through the DEA) must consider the drug’s history and current pattern of abuse; scope, duration, and significance of abuse; and risk to public health. Once scheduled through this temporary scheduling process, a substance may remain on Schedule I for one year. The Attorney General then has the authority to keep the substance on Schedule I for an additional six months before it must be removed or permanently scheduled."
Sacco, Lisa N. and Finklea, Kristin M., "Synthetic Drugs: Overview and Issues for Congress," Congressional Research Service (Washington, DC: Library of Congress, October 28, 2011), p. 3.