The coins aren't in the wallet - they're in a completely transparent, publicly viewable account in the bitcoin block chain. Every transaction is visible to everyone. The wallet only contains the credentials that allow you to transfer the coins to another account. If the wallet was encrypted, and they were unable to access the credentials, then they cannot meaningfully seize the account since another copy of the credentials could (and should) exist elsewhere allowing someone else to spend the coins.
Given that according to TFA, the Feds have already transferred the coins to another account that they hold and that the transfers are a part of the current accepted blockchain, I would say that they have seized them. A side effect is that by revealing the blockchain entry for the transfers, they have marked these coins as government owned and traceable for the rest of their existence.
I wonder if it would be possible to also transfer the coins using a blockchain prior to the Fed transfer, then somehow replace the Fed transfer in the current blockchain and get the majority to accept the substitution, effectively denying the Feds their seizure? I realize that the majority design of Bitcoin is meant to prevent this sort of thing in reality, but it should be theoretically possible, right?