Yes, this is possible through limiting privilege of the various categories, as well as potentially a custom bit of javascript to redirect users to the login page.
@juan-g If I’m not wrong this is only for groups. Anybody can't make subforum both with his own group.
This is interesting idea for plugin or like a feature for new version of core nodebb.
Good for wide community forums on autopilot, when owner not have enough time to support all desires of members.
