Consider a Sakai instance configured with the property:
Ie. this property controls Worksite Setup -> New -> Course Site, so that the displayed academic terms are filtered to contain only those in which the user has enrollments
Only users whose user role has site.add.course can get to this view (in Sakai OOTB, we have 'registered', for instance). However, if a 'registered' user has only student enrollments in a particular academic term, and they have no instructor enrollments in that academic term, the academic term can still be selected.
In the academic term dropdown, an academic term should only be presented to the user if the user has at least one section membership in the term whose role's template (in !site.template.course) has both 'site.upd', and 'realm.upd' (the permissions required to attach a section).