Act of Military Service for Volunteer Enlisted Soldiers (Amended) 
Owing to the Military needs of the National Defense, the following persons may volunteer to participate in the selection, receiving basic training with completing qualified service, taking to Volunteers Enlisted Soldiers:
1. Being inducted to take Standing Soldier Service in the military camp or Substitute Services.
2. Reserve Service of Standing Soldier.
3. Other nationals of the statutory age.
People from Mainland China and Hong Kong, Macao residents should be set up in Taiwan, the membership of less than 20 years before they may participate in the selection of the Volunteers Enlisted Soldiers.
The selection of Volunteers Enlisted Soldiers should consider the military required expertise; their selection criteria, procedures, and the camp program, training, assessment and retire training camp remain in service conditions and other relevant issues shall be determined by the Ministry of National Defense.
志願士兵服役條例 (民國 102 年 01 月 02 日 修正)
第 3 條
The interpretation of "nationals" (short for "ROC nationals") is the question here.
The last part indicates that there should be a subsidiary regulation in the MND's database that doesn't necessarily have the parent law in its title but mentions in its first Article that it's established in accordance with the parent law.