Civil Aviation Act Article 5

The first inbound landing of an aircraft originating from any point in a foreign country, or an outbound aircraft taking off from the ROC to another country, shall conduct such landing or takeoff at a designated international airport. A special approval granted by MOTC or in case of an emergency may be an exception.
中文原文 民用航空法第5條
航空器自外國一地進入中華民國境內第一次降落,及自國境內前往外國一地之起飛,應在指定之國際航空站起降。
但經交通部核准或緊急情況時,不在此限。

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