What is the legal argument that a search conducted at a border is justified?

2 Without attempting to specify any source of authority for the search conducted in this case, the majority suggests that "a search made at a border is justified by the need of the sovereign to protect itself," at 977 n. 7, citing United States v. Ramsey, 431 U.S. 606, 616, 97 S.Ct. 1972, 1978, 52 L.Ed.2d 617 (1977). This attempted justification cannot succeed, since the present case concerns the propriety of a search of a person leaving rather than entering the country. While it is hardly necessary to elaborate the illogic of a suggestion that searches of travelers leaving the United States are necessary to insure this country's safety, it is worth noting that the cited passage in Ramsey itself incorporates this distinction. It states that "searches made at the border, pursuant to the longstanding right of the sovereign to protect itself by stopping and examining persons and property crossing into this country, are reasonable simply by virtue of the fact that they occur at the border...." 431 U.S. at 616, 97 S.Ct. at 1978 (emphasis added).