But, the reason for this agency coming into being was much broader than to knight a batch of domestic "narcs." The domestic aspect represented only one tentacle; the one that Americans see. Actually, the lion's share of investigative and "enforcement" work done in the domestic war on drugs is conducted by state and local officers. They often act with federal funding and equipment and occasionally access federal prosecution with accompanying federal minimum mandatory sentencing rules. These state and local officers also often make use of less restrictive federal asset forfeiture mechanisms via federal "adoptions" of their seizures. But they are not DEA agents.
What then, other than the domestic war on drugs, is the DEA's purpose? The DEA, while a relatively small federal law enforcement agency, has many more foreign offices than any other. The FBI dwarfs the DEA in overall number of agents, but has few foreign offices. The DEA can get into places, obtain diplomatic cover, and run networks of confidential spies that the CIA, the military, and the FBI cannot because the DEA has no stated political mission, regime toppling imperative, or anti-corruption mandate as do its sister agencies. The FBI has relatively few foreign posts and even fewer that are staffed with active investigative personnel; the main exceptions being occasional showy importations to "hotspots" that have the potential for media headlines. FBI foreign assignments consist mostly of single-man suit-adorned supervisory "Legal Attaché" assignments in a relatively small number of U.S. embassies. These negligible foreign FBI posts don't have teams of investigative agents assigned with the paramilitary infrastructure (aircraft, weapons, and dedicated teams of foreign officials) and imbedded sources needed to carry out covert or overt missions in those places.