8 CFR 273.3 - Screening procedures.
(b) Procedures at ports of embarkation. At each port of embarkation carriers shall take reasonable steps to prevent the boarding of improperly documented aliens destined to the United States by taking the following steps:
(1) Screening of passengers by carrier personnel prior to boarding and examination of their travel documents to ensure that:
(i) The passport or travel document presented is not expired and is valid for entry into the United States;
(ii) The passenger is the rightful holder; and
(iii) If the passenger requires a visa, the visa is valid for the holder and any other accompanying passengers named in the passport.
(2) Refusing to board any passenger determined to be improperly documented. Failure to refuse boarding when advised to do so by a Service or Consular Officer may be considered by the Service as a factor in its evaluation of applications under § 273.5.
(3) Implementing additional safeguards such as, but not necessarily limited to, the following:
(i) For instances in which the carrier suspects fraud, assessing the adequacy of the documents presented by asking additional, pertinent questions or by taking other appropriate steps to corroborate the identity of passengers, such as requesting secondary information.
(ii) Conducting a second check of passenger documents, when necessary at high-risk ports of embarkation, at the time of boarding to verify that all passengers are properly documented consistent with paragraph (b)(1) of this section. This includes a recheck of documents at the final foreign port of embarkation for all passengers, including those originally boarded at a prior stop or who are being transported to the United States under the Transit Without Visa (TWOV) or International-to-International (ITI) Programs.
(iii) Providing a reasonable level of security during the boarding process so that passengers are unable to circumvent any carrier document checks.