VCS rejects offline operations if the procedure violates existing group dependencies. Typically, firm dependencies are more restrictive to taking child group offline while parent group is online. Rules for manual offline include:
Parent group offline is never rejected.
For all soft dependencies, child group can go offline regardless of the state of parent group.
For all firm dependencies, if parent group is online, child group offline is rejected.
For the online local hard dependency, if parent group is online, child group offline is rejected.