CBP officers must determine the nationality of each applicant for admission and, if determined to be an alien, whether or not the applicant meets the requirements of the Immigration and Nationality Act for admission to the United States.

U.S. Customs and Border Protection (CBP) officers in 2026 are trained to detect a wide array of threats, focusing on undeclared prohibited items, immigration violations, and signs of illicit activity. At primary inspection, they look for agricultural products (fruits, meats, or soil) that could carry pests, as well as currency exceeding $10,000 that hasn't been reported. Under the updated Directive 3340-049B implemented in January 2026, officers also conduct "Basic" and "Advanced" searches of electronic devices (smartphones, laptops, and even vehicle infotainment systems) to identify child exploitation material, evidence of financial crimes, or national security threats. Beyond physical goods, CBP uses behavioral analysis to spot "nervous" or "evasive" behavior that might suggest smuggling or human trafficking. Their goal is to facilitate legal trade and travel while maintaining a strict "biosecurity" and "national security" perimeter.