The decision in United States v Arnold by a three-judge panel reverses a U.S. District Court decision that said such searches require reasonable suspicion.

The case concerns Michael Arnold, who arrived at Los Angeles International Airport from the Philippines and was pulled aside by customs agents for a random laptop search. When the officers started up the computer they found two folders on the desktop labeled Kodak Pictures and Kodak Memories.

When they found photos of nude women in those folders, they spent several hours opening multiple files until they found images of child pornography. They seized the computer and two weeks later obtained a warrant. A grand jury charged Arnold with breaking federal child-pornography laws.

Border Rules Apply

In its ruling, the Ninth Circuit held that international arrivals at U.S. airports are subject to the same rules as border crossings. Those rules give customs officials broad leeway to conduct searches of anything a traveler brings into the country. The international terminal of a U.S. airport is the "functional equivalent of a border," the court said, citing the U.S. Supreme Court case of Almeida-Sanchez v. United States.

In arguments before the court, Arnold's lawyer, Marilyn Bednarski, had a creative argument to get around the presumption that border searches are reasonable. Computers are "an extension of ourselves," she told media outlets this week. "It really is like looking into someone's mind, rather than looking into a box or a folder or a purse."

In other words, Bednarski argued, laptops are actually an extension of our bodies. That argument is based on a Supreme Court holding that there is at least one limit to border officers' ability to search at will. In a 1985 case, United States v. Montoya de Hernandez, the Supreme Court ruled that officers do need reasonable suspicion to search the alimentary canal because "the interests in human dignity and privacy which the Fourth Amendment protects forbid any such intrusion on the mere chance that desired evidence might be obtained."

The appeals court didn't buy that argument.

Laptop Not a Home

Bednarksi also argued that the laptop was the equivalent of one's home, since it potentially contains digital versions of all the images and documents traditionally kept in the home. In another 1985 case, California v. Carney, the Supreme Court ruled that not even a mobile home is accorded the same privacy interest as an actual home since it is "readily movable." A laptop is even more movable than a mobile home, the court noted.

International travelers uncomfortable with having their laptops searched might want to consider storing files online and renting a laptop when they get to their destination country, or encrypting their files if they do travel with a laptop.

"It's so easy to encrypt your files, passing through any spot where you are liable to be searched with sensitive data unencrypted seems brain-dead," one person posted on a blog.