The 100-Mile Border Zone

U.S. law gives Customs and Border Protection (CBP) special authority to conduct immigration checks within 100 miles of any U.S. border or coastline — without needing a warrant. This area is called the "100-mile border zone." The zone is measured from every U.S. border: the U.S.–Mexico border, the U.S.–Canada border, and all U.S. coastlines — the Atlantic Ocean, Pacific Ocean, Gulf of Mexico, and the Great Lakes shoreline. Approximately 2 out of 3 people living in the United States — about 200 million people — live within this zone. Many of the country's largest cities are entirely inside it.

The United States has three levels of CBP authority based on where you are: At the actual border (ports of entry, border crossings, airports): CBP has the broadest authority. They can search you and your belongings without any suspicion. In the 100-mile zone: CBP can stop and briefly question you without a warrant, but they still need reasonable suspicion for a full search, and a judicial warrant to enter your home. The Fourth Amendment applies, but with reduced protections. More than 100 miles from any border or coast (the interior): Standard law enforcement rules apply. Immigration enforcement generally requires a warrant or probable cause.