Do you have any suggestions on how much "taint" is sufficient to authorize a "lock"? Will the output have to be proven to be 100% entirely from the MtGox theft? Maybe anything more than 90% tainted should be locked? Really since we are using 50% of the hashing power to enforce the rules, perhaps we should consider anything more than 50% tainted should be locked. Come to think of it, given the "ethical imperative" and the "massive fraud or theft", I suppose the best thing to do is consider anything more than 0.1% tainted to be lockable. It should be acceptable to temporarily lock valid bitcoins to protect the community from assisting the thief.
So glad to see that this idea is being taken seriously
This raises an interesting point though. My original proposal was only to lock coins presently belonging to Mt. Gox. I don't think it would be wise to lock coins belonging to others which might have been derived from stolen Mt. Gox coins, as this does become an even harder problem from an evidence point of view. Also, those others are not presently under legal action concerning the missing coins, whereas Mt. Gox is.
Clearly the evidentiary standards would need to be seriously considered.
You raise a good point though that this really is up to the miners. Sounds like the lock would be technically feasible, actually, not that hard.
10 of those "Gox coins" are mine! How about we lock them where they belong, back on my paper wallet. I deposited them after the withdrawal stoppage, so I know damn well they have not left Gox's pocket!
Here's an example of a user that might benefit from this. With the Gox coins locked, at least they wouldn't be stolen or leaked to someone else until after the court proceedings.