Still allow legacy triggers, feedback:

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/11910#note_31632911

app/services/ci/create_pipeline_service.rb

@@ -23,10 +23,6 @@ module Ci
         return error('Insufficient permissions to create a new pipeline')
       end
 
-      if trigger_request && !trigger_request.trigger.owner
-        return error('Legacy trigger without a owner is not allowed')
-      end
-
       unless branch? || tag?
         return error('Reference not found')
       end
@@ -63,7 +59,9 @@ module Ci
     def triggering_user_allowed_for_ref?(trigger_request, ref)
       triggering_user = current_user || trigger_request.trigger.owner
 
-      Ci::Pipeline.allowed_to_create?(triggering_user, project, ref)
+      (triggering_user &&
+        Ci::Pipeline.allowed_to_create?(triggering_user, project, ref)) ||
+        !project.protected_for?(ref)
     end
 
     def process!

spec/services/ci/create_pipeline_service_spec.rb

@@ -415,10 +415,10 @@ describe Ci::CreatePipelineService, services: true do
         let(:user) {}
         let(:trigger_request) { create(:ci_trigger_request) }
 
-        it 'does not create a pipeline' do
+        it 'creates a pipeline' do
           expect(execute_service(trigger_request: trigger_request))
-            .not_to be_persisted
-          expect(Ci::Pipeline.count).to eq(0)
+            .to be_persisted
+          expect(Ci::Pipeline.count).to eq(1)
         end
       end
     end