Civil Aviation Act Article 79

A foreign civil air transport enterprise may operate its aircraft on a non-scheduled flight between a point in the ROC and a point outside the ROC carrying passengers, cargo and mail with or without remuneration only after obtaining approval from the CAA.
中文原文 民用航空法第79條
外籍民用航空運輸業,須經民航局許可,其航空器始得飛航於中華民國境內之一地與境外一地之間,按有償或無償方式非定期載運客貨、郵件。

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