1987 Constitution of the Philippines
Section 22. The heads of departments may, upon their own initiative, with the consent of the President, or upon the request of either House, as the rules of each House shall provide, appear before and be heard by such House on any matter pertaining to their departments. Written questions shall be submitted to the President of the Senate or the Speaker of the House of Representatives at least three days before their scheduled appearance. Interpellations shall not be limited to written questions, but may cover matters related thereto. When the security of the State or the public interest so requires and the President so states in writing, the appearance shall be conducted in executive session.