He says that the law is clear: when you cross the border to enter the US, or land at an airport or seaport after an international plane or boat trip, you have not been admitted to the US yet. The Fourth Amendment does not apply completely, specifically the agent does not need a warrant or probable cause to search you or your belongings accompanying you (luggage, car, etc.). However, the search must be “reasonable”, and any search of your person (i.e. body search) must be based on “reasonable suspicion”. This is not mearly CPB policy or opinon, but in fact settled law based on U.S. Supreme Court rulings (this last part, I looked up myself).

Lyn Greenhill, you are correct that when you cross the border you are protected from “unreasonable” search and seizure, but the agents are simply not legally required to have a warrant. They must mearly conduct “reasonable” searches (if you’re saying that any such search is not reasonable without a warrant or probable cause, it suffices to say that the courts disagree).

Now, with respect to laptops, the legal question is whether searching electronic materials requires “reasonable suspicion” (as distinct from mearly a reasonably initiated and conducted search, which is always required), that is, should such searches be regarded as invasive enough to be treated as equivalent to a body search. That is, can CPB agents search your laptop without “reasonable suspicion” (i.e. without any suspicion needed for justification). From what I’ve learned, no serious legal argument is being made that would require a warrant or probable cause to search laptops at a border crossing (at least no serious legal argument that has not already been rejected by the courts), notwithstanding the ACLU press release.