From HEXONET Wiki
Transfer / Trade NACK by:
In the case that a transfer / trade needs to be canceled, this can be done by different parties:
REGISTRY: Means that the domain-registry is able to approve the transfer.
REGISTRAR: Means that the losing registrar is able to deny the transfer.
REGISTRANT / CUSTOMER: In some cases, the registrant is able to cancel a transfer / trade.
BOTH: Both parties are able to cancel the transfer.
NONE: Nobody has to approve the transfer.