From the Document: "The federal government has broad authority over the admission of non-U.S. nationals (aliens) seeking to enter the United States. The Supreme Court has repeatedly held that the government may exclude such aliens without affording them the due process protections that traditionally apply to persons physically present in the United States. Instead, aliens seeking entry are entitled only to those procedural protections that Congress has expressly authorized. Consistent with this broad authority, Congress established an expedited removal process for certain aliens who have arrived in the United States without permission."
CRS Report for Congress, R45314
Congressional Research Service: https://crsreports.congress.gov/