Monday, a federal appeals court’s ruling upheald earlier decisions that the border search doctrine does not require that fourth amendment protections be granted to citizens returning to the U.S. after traveling abroad. Laptops, hard drives, flash drives, digital cameras, cell phones, and other electronic media can be searched, copied, or sezied by customs officials without probable cause.

Although most seasoned travelers already know about this exception to their fourth amendment rights, the recent appeals case argued that a laptop was a “mobile home” and should be exempt from the exception. The “Washington Post” reported earlier this year on two citizens that were affected. One was asked to enter a password on a company laptop, and another had a laptop confiscated.

The Asian Law Caucus, in their document “Tips for travelers returning to the United States“, indicates that if you’re a citizen you can’t be denied re-entry into the country as long as you can prove that you’re a citizen. However, not giving up a password could delay your entry and lead to confiscation.

The Asian Law Caucus goes on to recommend backing up your documents before leaving the U.S., encrypting documents, using software that securely erases sensitive documents to prevent forensic analysis, and sending any documents in an encrypted form back to the U.S. before returning. If you are subjected to an inspection by customs agents, you should also ask whether any of your documents were copied and and get a receipt for any property that is seized.

I would recommend against bringing any proprietary or personal electronic documents with you. This means that after backing up any such files, wiping them completely from the devices that will be traveling with you by using software that can remove all forensic traces of the data. A fresh installation of your preferred operating system along with a JAVA enabled Web browser and properly exported SSL should be all you need. You should be able to do everything you need remotely via a virtual private network to the office.

The customs agents of both countries, with a copy of your encrypted files, will likely have the resources needed to crack your encryption some day. This is a lot more troubling to me than the idea of a typical thief getting ahold of your currently strong encrypted documents.

Don’t forget to clear your browser history, browser temporary files, and any browser cookies before returning. Also, be as courteous and helpful as possible to the customs agents for the best results.