Which branch of the U.S. government oversees HSI?

The correct answer is that the Department of Homeland Security oversees HSI (Homeland Security Investigations). HSI is a critical component of the Department of Homeland Security, which was established in response to the events of September 11, 2001, to consolidate various agencies focused on securing the nation's borders and protecting against threats. HSI specifically deals with investigating and enforcing immigration and customs laws, as well as tackling a wide range of crimes, including human trafficking, drug smuggling, and financial crimes.

The Department of Justice primarily focuses on enforcing the law and administering justice, including overseeing federal law enforcement agencies like the FBI. While the FBI and HSI may collaborate on certain investigations, they operate under different jurisdictions and missions. The Department of State is involved in international relations and diplomacy, rather than domestic law enforcement or border protection, and therefore does not oversee HSI's operations. This context highlights the specific alignment of HSI within the framework of the Department of Homeland Security and its focus on national security and law enforcement efforts.