Here the seizure of respondent took place at the international border. Since the founding of our Republic, Congress has granted the Executive plenary authority to conduct routine searches and seizures at the border, without probable cause or a warrant, in order to regulate the collection of duties and to prevent the introduction of contraband into this country. See United States v. Ramsey, 431 U.S. 606, 616 -617 (1977), citing Act of July 31, 1789, ch. 5, 1 Stat. 29. This Court has long recognized Congress’ power to police entrants at the border. See Boyd v. United States, 116 U.S. 616, 623 (1886). As we stated recently:
"`Import restrictions and searches of persons or packages at the national border rest on different considerations and different rules of constitutional law from domestic regulations. The Constitution gives Congress broad comprehensive powers "[t]o regulate Commerce with foreign Nations," Art. I, 8, cl. 3. Historically such broad powers have been necessary to prevent smuggling and to prevent prohibited articles from [473 U.S. 531, 538] entry.'" Ramsey, supra, at 618-619, quoting United States v. 12 200-Ft. Reels of Film, 413 U.S. 123, 125 (1973).
Consistently, therefore, with Congress’ power to protect the Nation by stopping and examining persons entering this country, the Fourth Amendment’s balance of reasonableness is qualitatively different at the international border than in the interior. Routine searches of the persons and effects of entrants are not subject to any requirement of reasonable suspicion, probable cause, or warrant, 1 and first-class mail may be opened without a warrant on less than probable cause, Ramsey, supra. Automotive travelers may be stopped at fixed checkpoints near the border without individualized suspicion even if the stop is based largely on ethnicity, United States v. Martinez-Fuerte, 428 U.S. 543, 562 -563 (1976), and boats on inland waters with ready access to the sea may be hailed and boarded with no suspicion whatever. United States v. Villamonte-Marquez, supra.
Balanced against the sovereign’s interests at the border are the Fourth Amendment rights of respondent. Having presented herself at the border for admission, and having subjected herself to the criminal enforcement powers of the Federal Government, 19 U.S.C. 482, respondent was entitled to be free from unreasonable search and seizure. But not only is the expectation of privacy less at the border than in the interior, see e. g., Carroll v. United States, 267 U.S. 132 , [473 U.S. 531, 540] 154 (1925); cf. Florida v. Royer, 460 U.S. 491, 515 (1983) (BLACKMUN, J., dissenting), the Fourth Amendment balance between the interests of the Government and the privacy right of the individual is also struck much more favorably to the Government at the border. Supra, at 538.