The Commercial Port Law Article 18

The master of a ship shall restrict the number of seafarers going ashore for leave, when his/her ship berths in port. The number of seafarers remained on board shall be sufficient to operate and navigate the ship and be capable of handling emergency events.
中文原文 商港法第18條
商港區域內停泊之船舶,其船員上岸休假,應由船長依規定予以限制。
留船人數應有足以操縱船舶航行及應付緊急事變之能力。

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