Which section grants the right to conduct border searches at fixed border entries and vessel document checks?

The section that grants the right to conduct border searches at fixed border entries and vessel document checks is indeed 19 USC § 1581. This provision outlines the authority of customs officers and other designated authorities to perform searches at international borders to enforce customs laws. It specifically provides guidelines and the legal ground for inspecting cargo and passengers entering the United States, thereby ensuring compliance with customs regulations.

This authority is crucial for maintaining national security and preventing illegal activities, such as smuggling and trafficking, at points where goods and individuals are entering the country. By specifying the rights of officials to conduct such inspections, the statute supports the broader objective of managing and regulating commerce across borders effectively.

The other options pertain to different aspects of immigration enforcement and authority but do not specifically address the scope of customs inspections or searches at borders in the same way. They may involve other enforcement powers and procedures but are not relevant to fixed border entry searches and vessel document checks as outlined under 19 USC § 1581.