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. 472. The international legal assistance may be refused if the granting of the request could endanger the sovereignty, national security, public order or other interests protected by law.
Refusal of ICC request
Refusal of ICC request - protection of national security
EDIT.