The Department of Homeland Security recently clarified its position to restate that if you cross the border, any of your digital information devices can be seized and searched without the government giving you any reason whatsoever. They did promise to try to return them in a more timely manner. This incldues everything from a laptop to an iPod to a USB flash drive. (Wow, wonder how many flash drives are in the pockets of my laptop bag now?)
So how many hours have you wasted trying to find a file on your computer that you knew was there? How long would it really take to search a laptop hard drive if you were a Homeland Security agent and didn't know for sure what you were looking for? The smart money is betting that in 90+% of the situations they will just make a complete image of your hard drive and then return it, retaining all of your information (and your client's information) "indefinitely."
Many, if not most, lawyers who carry laptops have some form of a "paperless" law practice and carry many client files on their laptops, hopefully encrypted or, at least, password protected. One of the nice things about having a laptop is using it as a desktop replacement to carry everything with you.
That laptop probably can no longer travel across the U.S.border with you. Whether top military grade encryption protects your information from the Department of Homeland security or just presents a professional challenge for them is for you to decide.
But, if you just need access to a few files and know you will have Internet access at your destination, you can always just e-mail them to yourself and leave them in your inbox. You could also use an online document repository or VPN or one of several other secure solutions for remote access to files.
Bottom line: These rules probably give every law firm a great justification to buy a Netbook or two for overseas travel. Cleaning up every confidential file from a laptop used as a primary workstation before traveling overseas would be too big a pain and cost more in lawyer time than a Netbook.