Regulations for the Review of Standardized Geographic Names and the Management of Geographic Names Article 4

Standardized geographic names shall be established in the Chinese language. For those names not represented in characters, suitable Chinese characters shall be chosen based upon its phonetic spelling.
中文原文 標準地名審議及地名管理辦法第4條
標準地名之訂定應以中文為之;無文字表示者,以拼音方式,擇其適當之中文定之。

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