Authorities need a search warrant to get at a computer in your home, and reasonable suspicion that you're up to no good to search your laptop in other places (like if you're surfing bomb-making sites while using WiFi at a coffee shop). But the rules change when you're crossing the border back into the United States. And that has raised concerns from business travelers, privacy advocates and some lawmakers about the vulnerability of the huge amounts of information people carry on their laptops and other digital devices. The legality of the practice hinges around whether searching a laptop is the equivalent of looking in your luggage, or more like a strip search. U.S. Courts have ruled, as recently as this spring in a case stemming from a search at LAX , that there's no need for warrants or suspicions when a person is seeking to enter the country because any "routine search" is reasonable under the Fourth Amendment. In effect, it's like luggage: anything and everything in your laptop, cellphone, BlackBerry or digital camera can be examined and copied by U.S. Customs and Border Protection agents. So far, the agency, part of the Department of Homeland Security, has been vague about when and why it conducts those digital searches, how long it keeps the information and what is done with it. Sen. Russ Feingold, a Wisconsin Democrat, wants to change that. At a congressional hearing he chaired on the issue today, he said: "I guarantee yo ...