Customs Personnel Management Act Article 9

If customs officers and the personnel working on the Customs affairs at the Ministry of Finance (hereinafter referred to as the MOF)possess required qualifications, they may be transferred to take up equivalent positions; the regulations concerning transfer shall be promulgated by the Ministry of Civil Service and the MOF.
中文原文 關務人員人事條例第9條
關務人員與財政部關政單位人員,得相互轉任相當職務,但以具有所轉任職務之任用資格者為限;其轉任辦法,由銓敘部會同財政部定之。

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