Which of the following best describes the authority provided under INA 287(a)(3)?

The authority provided under INA 287(a)(3) specifically grants Border Patrol agents the ability to conduct linewatch operations. Linewatch involves monitoring and patrolling the U.S.-Mexico border to observe and interdict illegal activities such as human smuggling and drug trafficking. This type of surveillance is crucial for maintaining the security of the borders and enables agents to respond to incidents as they occur.

The other options do not accurately reflect the specific provisions of INA 287(a)(3). For example, while customs inspections are covered under different statutes related to Customs and Border Protection, they are not encompassed by this particular INA section. Similarly, roving patrols and checkpoints fall under different operational guidelines and authority, which do not directly correlate with the linewatch authority defined in the specified INA subsection. Understanding the distinctions between these operations is important for recognizing the scope and application of border enforcement authority.