BULGARIA - PENAL PROCEDURE CODE
Part two. EVIDENCING
Chapter thirty six. PROCEDURES IN CONNECTION WITH INTERNATIONAL COOPERATION ON PENAL CASES
Section III. International Legal Assistance in Penal Cases
Art. 471. (1) International legal assistance in penal cases of another state shall be rendered on the terms of a concluded international treaty to which the Republic of Bulgaria is a party, or on the principle of mutuality. International legal assistance in penal cases shall also be rendered to an international court of justice whose jurisdiction has been recognised by the Republic of Bulgaria.
(2) The international legal assistance shall include:
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5. other forms of legal assistance if they are stipulated in an international treaty to which the Republic of Bulgaria is a party, or are imposed on the terms of mutuality.
Other types of assistance - national procedures for ICC proceedings
EDIT.