If you are using Exchange Online, by default anonymous calendar sharing is enabled in the tenant.
To enable or disable it , you may access Microsoft 365 admin center, locate Settings>Org settings>Services>Calendar and modify the settings of Allow anyone to access calendars with an email invitation.
If it is disabled, when users try to share calendar to anonymous users, they would receive an error message saying they don't have permission.
If you would to control which users can share calendar to anonymous users, or configure other settings like which information can be shared, you may also configure and assign sharing policy to specific users.
Also what possible ramifications would exist if we disallowed calendar sharing?
To me there should not be other effects besides that users won't be able to share their calendars with others.
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