Armed Forces Uniforms Act Article 7

Non-active duty servicemen are entitled to wear the uniforms stipulated by this Act on the following occasions:Subparagraph 1servicemen retired or out of commission being invited by the Ministry of National Defense to attend ceremonies;Subparagraph 2reservists being promoted;Subparagraph 3other circumstances approved by the Ministry of National Defense.
中文原文 陸海空軍服制條例第7條
非現役軍人有下列情形之一者,得穿著本條例所定之制服:
一、退伍、除役軍人經國防部邀請參加慶典。
二、後備軍人依法晉任授階。
三、其他經國防部核准者。

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