Back to the missing Bitcoins and the original question. Identify the Bitcoins and stop them in their tracks. Whether double spent or stolen, mine are mine and if MtGox sent them to someone else that's theft.
Who has the motivation to do that work though?
No one at MtGox. So, the government? Isn't it more in their interest to just tell you that bitcoin is not regulated, until they are ready to use the outrage to insist upon regulation?