[lmm]

And yet there are cases where the US constitution leads to this kind of weirdness. Safes in the US use combinations rather than keys (unlike most of the world), because bizarrely enough the authorities can (AIUI) get a warrant that forces you to give up a key, but not (or it's harder) to force you to disclose a combination. So it's not so implausible that there would be a similar legal technicality that was relevant here.