As mentioned in this blog post, the domain transfer was done as part of an international operation against the Avalanche botnet. As such, it was a legal action

As mentioned in this blog post, the domain transfer was done as part of an international operation against the Avalanche botnet. As such, it was a legal action as opposed to an administrative action. Further, the action was taken at registry level as opposed to registrar level (which is one level lower than the registry). Therefore, no EPP code was necessary and the "clientTransferProhibited" domain transfer record was ignored.