For example, the Court has ruled that it is not a “search” under the Fourth Amendment if police use a dog to sniff the exterior of luggage that police have temporarily seized in an airport terminal, believing that it is likely to contain something illegal. It also has allowed police to check the outside of a vehicle that police have legitimately stopped at a highway checkpoint set up to search for illegal drugs, or to check the outside of a vehicle that police have legally stopped for a suspected traffic violation. In each of those situations, the impact on privacy was considered to be very slight, because the intrusion was minimal, so the use of the dog did not violate the Fourth Amendment.