The "Combating Illicit Xylazine Act" aims to address the growing concern of illicit xylazine use by formally adding it to the definitions within the Controlled Substances Act (CSA) and placing it under Schedule III . This scheduling is intended to regulate the substance more strictly, thereby curbing its diversion and misuse while preserving its critical role in veterinary medicine. A key provision of the bill redefines the term "ultimate user" specifically for xylazine, ensuring that veterinarians, pharmacies, government animal control programs, and wildlife programs can lawfully possess and dispense it for animal care. This clarification extends to entities like government agencies or businesses with animals and their employees, allowing for continued legitimate use without requiring individual registration for ultimate users. To facilitate a smooth transition, the bill includes several amendments, such as delaying the effective dates for labeling, packaging, distribution logistics, and practitioner registration requirements. Existing manufacturers are also exempt from immediate capital expenditures for new security standards, and federal agencies are directed to expedite necessary manufacturer submissions. The legislation further mandates the inclusion of xylazine in the Automated Reports and Consolidated Orders System (ARCOS) for tracking purposes. Finally, the bill directs the United States Sentencing Commission to review and amend sentencing guidelines for offenses involving xylazine, considering its various forms and co-use with other scheduled substances. It also requires the Attorney General, in coordination with the FDA, to submit two comprehensive reports to Congress on the prevalence, impacts, diversion, and proliferation of illicit xylazine use in the United States.