diff --git a/ietf/meeting/models.py b/ietf/meeting/models.py
index 8cf386abf29..8bfdefbd2be 100644
--- a/ietf/meeting/models.py
+++ b/ietf/meeting/models.py
@@ -1243,6 +1243,9 @@ def can_manage_materials(self, user):
     def is_material_submission_cutoff(self):
         return date_today(datetime.UTC) > self.meeting.get_submission_correction_date()
     
+    def is_past(self):
+        return timezone.now() > self.official_timeslotassignment().timeslot.end_time()
+     
     def joint_with_groups_acronyms(self):
         return [group.acronym for group in self.joint_with_groups.all()]
 
diff --git a/ietf/meeting/views.py b/ietf/meeting/views.py
index 913c8bd3021..adaeca11b2e 100644
--- a/ietf/meeting/views.py
+++ b/ietf/meeting/views.py
@@ -1931,7 +1931,11 @@ def api_get_session_materials(request, session_id=None):
 
     minutes = session.minutes()
     slides_actions = []
-    if can_manage_session_materials(request.user, session.group, session) or not session.is_material_submission_cutoff():
+    if (
+        has_role(request.user, "Secretariat")
+        or (not session.is_material_submission_cutoff() and session.can_manage_materials(request.user))
+        or not session.is_past()
+    ):
         slides_actions.append(
             {
                 "label": "Upload slides",
@@ -3546,6 +3550,12 @@ def upload_session_slides(request, session_id, num, name=None):
             "The materials cutoff for this session has passed. Contact the secretariat for further action.",
         )
 
+    if session.is_past() and not can_manage:
+        permission_denied(
+            request,
+            "This meeting has already occurred. Contact a chair or the secretariat for further action.",
+        )
+
     session_number = None
     sessions = get_sessions(session.meeting.number, session.group.acronym)
     show_apply_to_all_checkbox = (
diff --git a/ietf/templates/meeting/session_details_panel.html b/ietf/templates/meeting/session_details_panel.html
index 7c52ac0b4ab..62fda934705 100644
--- a/ietf/templates/meeting/session_details_panel.html
+++ b/ietf/templates/meeting/session_details_panel.html
@@ -185,7 +185,7 @@ <h3 class="mt-4">Slides</h3>
                href="{% url 'ietf.meeting.views.upload_session_slides' session_id=session.pk num=session.meeting.number %}">
                 Upload new slides
             </a>
-        {% elif request.user.is_authenticated and not session.is_material_submission_cutoff %}
+        {% elif request.user.is_authenticated and not session.is_past %}
             <a class="btn btn-primary proposeslides"
                href="{% url 'ietf.meeting.views.upload_session_slides' session_id=session.pk num=session.meeting.number %}">
                 Propose slides