I'm running out of ideas that don't fall under those ...
Maybe we need to be more creative in our thinking. What if the cold-storage wallet used a 2-of-3 signature transaction between Ukyo, someone that is off the grid and someone that has recently died or become unavailable? Or retrieving some signatures require some contractual requirement that cannot be disclosed? Or maybe even a block-height timeout in the transaction (not sure why he couldn't tell us this though... "you can all have your coins at block height 300000").
After reading today's
reddit post about protesting at MtGox (as foolish as that might have been), I realized that the need for secrecy around cold-storage wallets may have caused some entities to enter into non-disclosable contracts with counterparties, key escrow agents, etc. Security through obscurity sort of stuff.
Nope.
It's all about the laws of having a "Trust" with other peoples money.
The examples you gave don't matter.
If he has entered into an agreement with a 3rd party that isn't legal for him to do so, the agreement is null and void.
"Sorry I can't give them back to you yet" isn't a legal option.
As for MtGox - heh well - yeah that was quite a stir.
(and it's bullshit - it's been happening for 2 months)
They still have 1925 transactions pending and the rest forced back into the people's accounts for the weekend
(most likely MtGox see the opportunity of more transaction fees from that ...)