This may be over simplitying it
but if your front door was locked and the Law asked you to open but you didn't want to in case they found something naughty, saying no or you've lost your key isn't going to stop them. They would just bash your door in. If the Law has the time and access surely they can just use a brute force attack to "open" your encrypted data. To my mind we're not talking about authorities wanting to snoop but Law enforcement with a legitimate case for searching your property.
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