The district court judge has overruled the magistrate, holding that, while they cannot compel him to provide the password, they can compel him to provide an unencrypted copy of the encrypted volume without violating those rights. Seems like a distinction without a difference. Stay tuned.
One difference: if he uses his (still-secret) password to decrypt a copy of the material in question, the action only affects the material in question.
Whereas if he provides his password, he has effectively lost his privacy on ALL his so-encrypted data, whether it applies to this case or not. A much larger loss.
I use PGP/GPG for encryption of my private data, and while I would fight tooth and nail against relinquishing my passphrase, I would consider agreeing to decrypt selected content in a court case. Depends...
And of course, in any event, the minute I could do so, I would change the old passphrase associated with my private key to something else.