-You'd obviously need to be able to provide proof of your clearance* (though I suppose your passport and a database lookup would do) - but I wonder what would b

-You'd obviously need to be able to provide proof of your clearance* (though I suppose your passport and a database lookup would do) - but I wonder what would be the next step then; getting hold of an official with the required clearance to match the documents in your laptop? (Which, in the case of higher/compartmentalised clearances may not even be possible) At some point you just need to start trusting people. *) I wouldn't recommend leaving docs leaked by Ed Snowden on the laptop just to be able to rightfully claim there's classified material on it...