National Palace Museum Regulations for the Acquisition of Cultural Relics Article 15

The custody of cultural relics shall be made in the form of an agreement between the owner and the Museum. Cultural relics intended to be placed under the Museum’s custody shall be processed in accordance with the appraisal procedures outlined in Article 4. Those that are deemed unfit for the collection will be partially or entirely returned to the owners.
中文原文 國立故宮博物院藏品徵集辦法第15條
凡寄存文物,由本院與寄存者商訂詳細寄存方式並訂定合約,但須按第四條規定之程序辦理;其認為無寄存價值者,得部分或全部謝絕之。

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