Asset Recovery and Bitcoin

Hi,

Assume a fraudster parks his ill-gotten gains in a bank account. As part of fraud recovery proceedings, the court can issue a freezing order to freeze the fraudster's assets. In compliance with the order, the fraudster's bank will not allow any funds to be withdrawn from the impugned account.

What recourse is there if the fraudster parks his money in a Bitcoin wallet? Is there any way to obtain access to the BTC wallet, outside of the fraudster voluntarily giving up his public/private keys?

What if the fraudster uses an online wallet (e.g., blockchain.info)? If I understand correctly, in such cases, online wallets (i.e., public and private keys) are held by a third party (e.g., blockchain.info). Could such third parties be compelled to comply with a freezing or seizure order to hand over the keys? Or could their servers be searched to retrieve the keys?

Assuming the fraudster hosts (?) his own BTC wallet. Would seizing his physical hard drive give authorities access to public and private keys, and therefore his wallet?

Assuming the public/private keys cannot be found (i.e., either the fraudster will not cooperate or the keys cannot be recovered from his hard drive, his diary, etc.). Can authorities obtain the public/private keys by issuing subpoena to the ISP? Or through packet sniffing?

Basically, how can authorities get their hands on a fraudster's Bitcoin wallet, outside of the fraudster's cooperation?