首先，“treasury shares”意思很容易查到，库存股，是指已公开发行的股票但发行公司通过购入、赠予或其他方式重新获得可再行出售或注销的股票。Treasury stock, also known as treasury shares or reacquired stock refers to previously outstanding stock that is bought back from stockholders by the issuing company. The result is that the total number of outstanding shares on the open market decreases. These shares are issued but no longer outstanding and are not included in the distribution of dividends or the calculation of earnings per share (EPS).

若此处将retire译为回购，则大概意思则为库存股未予以回购，但是听起来会比较奇怪，因为回购之后的股份一般才会叫做库存股，因此，译为“回购”显然是不合逻辑的。

经搜索，retired shares的英文定义如下：

Retired shares are permanently canceled and cannot be reissued later. Once retired, the shares are no longer listed as treasury stock on a company's financial statements. Non-retired treasury shares can be reissued through stock dividends, employee compensation, or a capital raising.

这句话的大概意思是说，retired shares被永久注销，且之后不得再重新发行，一旦retired，则将不会再在公司的财务报表中以库存股的形式列示。未retired的库存股可以通过股息、员工薪酬或资本筹集重新发行。

因此，由上可知，很明显，retire在此处译为“注销”更为合适。同时，这也刚好与前文库存股的定义（“重新获得可再行出售或注销的股票”）相对应。

所以，全文可以译为：

必须注意的是，在Borg案中，库存股未被公司注销，股本未减少。