Under what specific legal authority can CBP conduct warrantless searches within the 'extended border' region of the U.S.?

CBP (Customs and Border Protection) can conduct warrantless searches within the 'extended border' region of the U.S. under the 'border search exception' to the Fourth Amendment. This exception allows federal agents to conduct searches of persons and property entering or exiting the country without a warrant or probable cause, based on the government's long-standing right to protect its borders and regulate the flow of goods and people. The 'extended border' is generally defined as a reasonable distance inland from the actual border, typically 100 miles, though this can vary depending on circumstances. This authority is based on the idea that individuals and goods entering the country have a reduced expectation of privacy, allowing CBP to conduct these searches to prevent illegal activities like smuggling or the entry of inadmissible persons. The Supreme Court has upheld the constitutionality of border searches, recognizing their necessity for effective border control.