I agree with @zoesqwilliams.bsky.social - nothing in the law requires exclusion. Whether you're the Women's Institute or the Girl Guides you have the option of just making your rules say you accept biological females and trans girls/women.
This is an act of choice, not legal necessity.
www.theguardian.com
Girlguiding’s response to last year’s supreme court ruling is not the humane option – and changes the organisation’s identity, says Guardian columnist Zoe Williams