They say they are legally being forced to, this headline is misleading
"We intend to be clear that whilst the law restricts membership, it's our firm organisational belief that transgender women are women," she said, adding it would continue to "express our continued sisterhood to transgender women" through the new network being set up.
https://www.lgbtqnation.com/2025/12/century-old-womens-group-forced-to-ban-trans-women-after-a-decade-of-inclusion/