National Emblem and National Flag of the Republic of China Act Article 16
The national emblem and flag shall be manufactured in domestic silk, wool, cotton, or linen.
中文原文 中華民國國徽國旗法第16條
國徽、國旗，以國產絲毛棉麻等織品為材料製造之。
English translation for reference only; the Chinese text prevails. Not legal advice.