diff --git a/awx/api/views.py b/awx/api/views.py
index db17f05c0d..158d4da1db 100644
--- a/awx/api/views.py
+++ b/awx/api/views.py
@@ -189,9 +189,22 @@ class InstanceGroupMembershipMixin(object):
                 ig_obj.save()
         return response
 
+    def is_valid_relation(self, parent, sub, created=False):
+        if sub.is_isolated():
+            return {'error': _('Isolated instances may not be added or removed from instances groups via the API.')}
+        return None
+
+    def unattach_validate(self, request):
+        (sub_id, res) = super(InstanceGroupMembershipMixin, self).unattach_validate(request)
+        if res:
+            return res
+        sub = get_object_or_400(self.model, pk=sub_id)
+        attach_errors = self.is_valid_relation(None, sub)
+        if attach_errors:
+            return (sub_id, Response(attach_errors, status=status.HTTP_400_BAD_REQUEST))
+
     def unattach(self, request, *args, **kwargs):
         response = super(InstanceGroupMembershipMixin, self).unattach(request, *args, **kwargs)
-        sub_id, res = self.attach_validate(request)
         if status.is_success(response.status_code):
             if self.parent_model is Instance:
                 ig_obj = get_object_or_400(self.model, pk=sub_id)
diff --git a/awx/main/models/ha.py b/awx/main/models/ha.py
index 6386857f08..e95378bb93 100644
--- a/awx/main/models/ha.py
+++ b/awx/main/models/ha.py
@@ -120,6 +120,8 @@ class Instance(BaseModel):
     def is_controller(self):
         return Instance.objects.filter(rampart_groups__controller__instances=self).exists()
 
+    def is_isolated(self):
+        return self.rampart_groups.filter(controller__isnull=False).exists()
 
     def refresh_capacity(self):
         cpu = get_cpu_capacity()
diff --git a/awx/main/tests/functional/api/test_instance_group.py b/awx/main/tests/functional/api/test_instance_group.py
index bac1c9a806..50c033b69b 100644
--- a/awx/main/tests/functional/api/test_instance_group.py
+++ b/awx/main/tests/functional/api/test_instance_group.py
@@ -2,6 +2,7 @@ import pytest
 
 from awx.api.versioning import reverse
 from awx.main.models import (
+    Instance,
     InstanceGroup,
     ProjectUpdate,
 )
@@ -14,6 +15,12 @@ def tower_instance_group():
     return ig
 
 
+@pytest.fixture
+def instance():
+    instance = Instance.objects.create(hostname='iso')
+    return instance
+
+
 @pytest.fixture
 def instance_group(job_factory):
     ig = InstanceGroup(name="east")
@@ -22,9 +29,11 @@ def instance_group(job_factory):
 
 
 @pytest.fixture
-def isolated_instance_group(instance_group):
+def isolated_instance_group(instance_group, instance):
     ig = InstanceGroup(name="iso", controller=instance_group)
     ig.save()
+    ig.instances.set([instance])
+    ig.save()
     return ig
 
 
@@ -113,3 +122,22 @@ def test_prevent_delete_iso_and_control_groups(delete, isolated_instance_group,
     controller_url = reverse("api:instance_group_detail", kwargs={'pk': isolated_instance_group.controller.pk})
     delete(iso_url, None, admin, expect=403)
     delete(controller_url, None, admin, expect=403)
+
+
+@pytest.mark.django_db
+def test_prevent_isolated_instance_added_to_non_isolated_instance_group(post, admin, instance, instance_group, isolated_instance_group):
+    url = reverse("api:instance_group_instance_list", kwargs={'pk': instance_group.pk})
+
+    assert True is instance.is_isolated()
+    resp = post(url, {'associate': True, 'id': instance.id}, admin, expect=400)
+    assert u"Isolated instances may not be added or removed from instances groups via the API." == resp.data['error']
+
+
+@pytest.mark.django_db
+def test_prevent_isolated_instance_removal_from_isolated_instance_group(post, admin, instance, instance_group, isolated_instance_group):
+    url = reverse("api:instance_group_instance_list", kwargs={'pk': isolated_instance_group.pk})
+
+    assert True is instance.is_isolated()
+    resp = post(url, {'disassociate': True, 'id': instance.id}, admin, expect=400)
+    assert u"Isolated instances may not be added or removed from instances groups via the API." == resp.data['error']
+