8 USC 1230 - Records of admission

(a) The Attorney General shall cause to be filed, as a record of admission of each immigrant, the immigrant visa required by section 1201 (e) of this title to be surrendered at the port of entry by the arriving alien to an immigration officer.
(b) The Attorney General shall cause to be filed such record of the admission into the United States of each immigrant admitted under section 1181 (b) of this title and of each nonimmigrant as the Attorney General deems necessary for the enforcement of the immigration laws.