Here are the list of nations and factions that part of the alliance.

1. Black Knights

2. United Federation of Nations (When Code Geass world united against common enemy)

3. Gallia (reformed by current ruler)

4. Daelaam

5. Terran Dominion

6. New Union State

7. United Allied Nation

8. Empire of the Rising Sun

9. Steelia/Brotherhood of Steel

10. Unified Earth Government

11. Galactic Species Alliance

12. Global Defense Initiative/Galactic Defense Initiative

13. USSR/Soviet Union

14. Kingdom of Vale (Only because the council decides to establish the military rather than rely on Atlas after they abandon them because their kingdom is being invaded)

15. United Territories of Commonwealth

16. Interplanetary Strategic Alliance 

17. Mobian Resistance

18. United Nation Space Alliance (UNSA)

19. United Federation/United Federation of Mobius