BULGARIA - PENAL PROCEDURE CODE
Part two. EVIDENCING
Chapter thirty six. PROCEDURES IN CONNECTION WITH INTERNATIONAL COOPERATION ON PENAL CASES
Section 1 Transfer of Convicted Persons
Art. 453. (1) The transfer of persons convicted by a court of the Republic of Bulgaria, for serving the punishment in the state whose citizens they are, and the transfer of Bulgarian citizens convicted by a foreign court, for serving the punishment in the Republic of Bulgaria, shall be decided by the Chief Prosecutor under an agreement with the competent authority of the other state, in the presence of consent in writing from the convicted person.
(2) The decision for the transfer of the convicted person may also be made after the execution of the punishment has started.
Surrender
Cooperation under procedures of national law
EDIT.