Regulations Governing Securities Borrowing and Lending by Securities Firms Article 12

A securities firm conducting securities borrowing and lending business may not lend, borrow, or accept as collateral, subject securities that are:1.Securities that are subject to a pledge; or2.Shares, or any other equity-type securities, of the securities firm itself that it acquires through share buybacks, gifts from others, mergers, transfer of business from others, or otherwise.
中文原文 證券商辦理有價證券借貸管理辦法第12條
證券商辦理有價證券借貸業務,有下列情形者,不得為借貸之標的或收受之擔保品:
一、設質之有價證券。
二、公司因買回、受贈、合併、營業受讓或其他原因取得之本公司股份或其他具有股權性質之有價證券。

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