Assing issues only to members of a group

Hi!
I am trying to configure a project in such a way that users of a certain group can assign issues to ONLY members of a defined group. Is there a way to do it without writing a plugin? Now I can see that the only thing one can do is to define a tracker where an issue gets assigned to a single defined user, not a member of a group... I am running Redmine 5.1.2.

Thanks in advance,