So I really want to know why it is that this does not seem to violate any laws (Tip of the hat to Pharyngula):
Federal agents may take a traveler's laptop computer or other electronic device to an off-site location for an unspecified period of time without any suspicion of wrongdoing, as part of border search policies the Department of Homeland Security recently disclosed. . . .
DHS officials said the newly disclosed policies -- which apply to anyone entering the country, including U.S. citizens -- are reasonable and necessary to prevent terrorism. Officials said such procedures have long been in place but were disclosed last month because of public interest in the matter.
You can view the policy here, which does contain partial exceptions for business information and attorney-client privileged material, and which does state that most of the information gathered (unless it relates to a crime) needs to be destroyed afterwards.
Now, I am not silly enough to let Firefox remember the password to my internet bank account, but anyone with access to my laptop could find their way into my email. Theoretically, when I enter the United States next month, immigration officials are allowed to look at every silly story or diary-like ramble in my 'documents' folder.
For some reason it doesn't bother me half so much that they're probably also allowed to read my paper diary if they wish. Electronic information is easily searched, easily copied, easily secreted, easily sent. Sure, you're supposed to destroy it all, but I bet that's unenforceable in practice. So I have to rely on the disinterest of customs officials and anyone else deemed necessary to decode my data. In my case, maybe that's not so bad. I'm not doing anything terribly secret or interesting, don't own any pornographic material of myself that could accidentally find its way onto the internet, and if all else fails, I'm white and I speak English and I bet that counts for more than it should in avoiding being searched in the first place. Travellers shouldn't have to rely on luck like that, though!
The Fourth Amendment, which I quoted in the post title, does not apply with the same force to border searches (see Wikipedia). Although they need reasonable suspicion to search me bodily, currently thay can search me mentally (via my laptop) for any reason or none. Frankly, I think I'd rather be searched bodily.
Although it will be to late to protect me, I hope Russ Feingold's plan to introduce legislation to stop this sort of thing is successful. Squick. Seriously, this is what I call an invasive search!