Even if he can't freeze it, he has access to the public ledger and with some effort can figure out who sent money to whom. Either of those two parties could then get a visit and politely invited to reveal the other.
If you want (more?) anonymous you need Monero or Zerocoin.
... and Putin has lots of thugs happy to wield USD$5 (RUB 388) wrenches to obtain those private keys, and the globally known precedent of the year-long torture & murder of Sergi Magnitsky to let the key-holders know that there's no way out.
He can if he's got the private key.