Generally, customs officers may stop people at the border to determine whether they are admissible to the United States, and they may search people's belongings for contraband. This is true even if there is nothing suspicious about you or your luggage.

Customs searches are usually triggered by a "risk model" or specific anomalies detected during X-ray screening. Common reasons include the presence of dense organic matter (like certain cheeses or meats), a jumble of tangled electronics and cables, or large quantities of liquids that look suspicious on the monitor. In 2026, customs officers also use advanced behavioral analysis; if a traveler appears overly nervous or provides inconsistent answers during the initial declaration, it can lead to a secondary inspection. Occasionally, you may simply be the victim of a "random" spot check used to ensure overall compliance. Prohibited agricultural items, undeclared currency over $10,000, or items that appear to be for commercial resale rather than personal use are the most frequent targets of these detailed physical searches at international borders.