For this to be true ther would have to be proof that he does in fact have the key to decrypt the device,otherwise they are holding him for not remembering the key. This is like asking a mute guy to speak up or be held indefinitely for contempt of court. The court should be required to prove that their demand is actually possible for the person in question before they can hold someone in contempt, otherwise they are just a kangaroo court.
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Do you have proof that remembers the key they ask for?