Code of Civil Procedure Article 306

Where a witness is or was a public officer and is to be examined with regard to the matter which he/she is obliged to keep confidential by virtue of his/her duties, he/she shall be examined with the permission of his/her supervising officer.The permission provided in the preceding paragraph may not be withheld except where a preliminary showing has been made that such examination will encumber national interests.
中文原文 民事訴訟法第306條
以公務員或曾為公務員之人為證人,而就其職務上應守秘密之事項訊問者,應得該監督長官之同意。
前項同意,除經釋明有妨害國家之利益者外,不得拒絕。

English translation for reference only; the Chinese text prevails. Not legal advice.