Für welche US Behörde arbeiten die Beamten, die bei der Einreise in die USA fragen, warum man in die USA reist?

Under the authority granted by the Immigration and Nationality Act (INA), as amended, a CBP officer may question, under oath, any person coming into the United States to determine his or her admissibility. In addition, an inspector has authority to search without warrant the person and effects of any person seeking admission, when there is reason to believe that grounds of exclusion exist which would be disclosed by such search. Quelle