Postal Act Article 47

The competent regulatory agency may assign Chunghwa Post to enter into, on behalf of the government, negotiations with foreign or international postal organizations with regard to international postal affairs and the signing of related protocols. Such negotiations shall be conducted in accordance with the relevant laws and regulations of the Republic of China.
中文原文 郵政法第47條
主管機關得委託中華郵政公司,代表政府與外國或國際郵政組織談判國際郵政事務及簽署有關協定;其協定事項,並應依相關法規規定辦理。

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