[gamblor956]

It's not strictly illegal. The government isn't asking you for your Bitcoins, its asking for your keys. It's like asking you for your account number but not the cash in the account. If the Government wanted to prevent the movement of your bitcoin assets, they would request an order barring outbound transfers. Alternatively, they'd simply move to seize the assets under some sort of forfeiture doctrine. (Forfeiture generally only applies to drug money or money acquired through the commission of a crime, but thanks to the Silk Road and other underground marketplaces, that will be the default presumption in most courts.)

In practice you'd be hard pressed to find prosecutors or judges who understand the conceptual difference between bitcoins and keys. The DoJ has a digital currency task force that is working on a legal blueprint for dealing with these sorts of issues, but it will be months before they get anywhere.