Fix federation! Closed federation should mean CLOSED.
GCC tenant has closed federation configured. All domains blocked except explicitly allowed domains. Users are unable to search for or communicate with external organizations as expected, HOWEVER, they are able to join conferences and share media with external organizations. Example: external organization creates a Teams call. GCC user is not invited. GCC user is accidentally forwarded the join URL, GCC user can actually join and participate in the externally hosted call, even though they are not federated. It's as if the federation list is only applicable to P2P calls, and not for MCU calls. Please fix this! This is a HUGE problem.
I believe AGAT Software has a solution for this