Which agency serves as the primary investigative authority for border enforcement and drug trafficking investigations?

Homeland Security Investigations (HSI) is the agency that serves as the primary investigative authority for border enforcement and drug trafficking investigations. HSI operates under the Department of Homeland Security and is responsible for enforcing customs laws, immigration laws, and various criminal laws related to border security and narcotics trafficking.

The agency conducts complex investigations that often intertwine with various aspects of transnational crime, including human smuggling, drug trafficking, and immigration violations. Given HSI’s broad jurisdiction and focus on threats to national security, it plays a crucial role in addressing issues that occur along the U.S. borders.

While other agencies, such as the DEA, have vital roles in drug enforcement specifically, HSI's scope includes a wider range of border-related matters, making it the primary agency for investigation in this area. HSI collaborates with other entities to effectively tackle threats that involve drug trafficking and enforcement at borders, further emphasizing its leading role in these investigations.