Combatting Illicit Drugs: DOJ and DHS Must Resolve Uncertainties Around Collaboration to Ensure Effective Counternarcotics Investigations

What GAO Found The Drug Enforcement Administration (DEA) and U.S. Immigration and Customs Enforcement (ICE) have entered into longstanding formal agreements to enhance their collaboration on counternarcotics investigations, including a June 2009 interagency cooperation agreement and a January 2021 joint letter. These agreements describe how DEA and ICE’s Homeland Security Investigations (HSI) are to coordinate on investigations. They establish requirements for DEA to cross-designate (or allow) HSI special agents to engage in counternarcotics investigations under the Controlled Substances Act and for both agencies to deconflict case information and engage in joint training, among other things. More recently, GAO found that the Department of Justice (DOJ) issued two new documents since 2021 that relate to DEA and HSI collaboration on counternarcotics investigations—a January 2025 DOJ Office of Legal Counsel opinion and a May 2026 memorandum from the Acting Attorney General. DOJ Documents Issued Since 2021 Related to DEA and ICE Collaboration Prior to the issuance of the May 2026 memorandum, GAO found that DEA and ICE’s collaboration generally addressed four out of eight leading collaboration practices, including defining common outcomes and clarifying roles and responsibilities. The four leading practices that DEA and ICE had not fully addressed (ensuring accountability, sustaining leadership, bridging organizational cultures, and updating agreements) involve activities require