Which agency is responsible for enforcing immigration laws at U.S. borders?

The responsibility for enforcing immigration laws at U.S. borders lies with U.S. Customs and Border Protection (CBP). This agency operates under the Department of Homeland Security (DHS) and plays a critical role in securing the nation's borders, ensuring lawful trade and travel, and enforcing immigration laws. CBP officers are stationed at ports of entry and border areas, where they are responsible for detecting unauthorized entries and apprehending individuals who are violating immigration regulations.

In contrast, while Immigration and Customs Enforcement (ICE) is involved in the enforcement of immigration laws, their primary focus is on investigating immigration violations and conducting removal operations within the interior of the United States rather than at the borders. The Federal Bureau of Investigation (FBI) primarily handles federal criminal investigations and counterterrorism efforts and is not focused on immigration enforcement at borders. The Department of Homeland Security, while encompassing both CBP and ICE, is a broader agency responsible for a range of activities related to national security, which makes it less specific in terms of the direct enforcement of immigration laws at borders compared to CBP. Thus, U.S. Customs and Border Protection is the most accurate choice for this particular question regarding border enforcement.