Originally Posted by Wikipedia
Whether a border search is reasonable depends on a judicial analysis that balances the intrusion into an individual’s legitimate privacy and dignity interests against the government’s legitimate interest in the subject of the search. In reviewing the reasonableness of border-searches under the Fourth Amendment, many courts have distinguished between "routine" and "nonroutine" searches. Customs may conduct "routine" searches without any level of suspicion, while "nonroutine" searches must be supported by "reasonable suspicion". Under this analysis, searches of a traveler's property, including luggage, briefcases, wallets, and other containers are "routine," while searches of a traveler's body, including strip, body cavity and involuntary x-ray searches, are considered "nonroutine."