In a decision that could anger some privacy advocates, a US appeals court said that border and airport security agents can search laptops without cause.

Surprisingly, the unanimous 3-0 decision came from the Ninth US Circuit Court of Appeals, which has otherwise been a target of criticism for its alleged liberal bias.

In Arnold's case, in 2005, border agents searched his computer after he had returned from the Philippines, finding it to contain child pornography. While he was released at the time, federal officials obtained a warrant for his arrest two weeks later.

Federal laws already allow border guards to search diaries and other personal items without cause. The Justice Department argues that electronic devices are no different, and should still be searchable as a matter of national security.

The appeals court argued that the Supreme Court had already ruled that there was no difference between searches of electronic devices and something like luggage, which is regularly done today.

Arnold's lawyers said they would appeal the verdict, which may now either be elevated to the Supreme Court, or stayed pending a petition for a rehearing before an appeals court.

The Electronic Frontier Foundation, which filed an amicus brief in support of Arnold's case, disagreed that laptop searches were any different from other common border searches.

"Fourth Amendment law constrains police from conducting arbitrary searches, implements respect for social privacy norms, and seeks to maintain traditional privacy rights in the face of technological changes," EFF civil liberties director Jennifer Granic said. "This Arnold opinion fails to protect travelers in these traditional Fourth Amendment ways."