I was able to locate this information in the Google Workspace updates:
Admins can now set the default access for new spaces and who can find them by defining the appropriate target audiences. While creating topic-based conversations that can be shared more broadly within an organization fosters collaboration and helps build community, there may still be instances where an organization may wish to target which group or audience can discover or join a space. With additional admin controls, admins can help users discover and join relevant conversations to encourage collaboration more effectively.
Getting started
- Admins: The creation of “Discoverable” spaces will be OFF by default and can be enabled at the domain level. Visit the Help Center to learn more about Google Chat sharing settings.
More info can be found here: https://workspaceupdates.googleblog.com/2022/06/admin-controls-for-discoverable-spaces-in-google-cha....
It looks like there are ways to control some aspects of Chat, like who can add Google Groups to Spaces. The admin can set the default for new spaces and define more granule target audiences for Discoverable S..., but there's currently no way for admins to disable creating Spaces.
If this doesn't solve the original question, please submit a feature request through the Admin Console.
Best ~ Kristal
Kristal D Ayres