At border crossings (also called "ports of entry"), federal authorities do not need a warrant or even suspicion of wrongdoing to justify conducting what courts have called a "routine search," such as searching luggage or a vehicle.
Even in places far removed from the border, deep into the interior of the country, immigration officials enjoy broad—though not limitless—powers. Specifically, federal regulations give U.S. Customs and Border Protection (CBP) authority to operate within 100 miles of any U.S. "external boundary."
In this 100-mile zone, Border Patrol agents have certain additional authorities. For instance, Border Patrol can operate immigration checkpoints.