Branch unprotection restriction starting point

Explored Policy framework to create something I can use as a starting point.

app/policies/protected_branch_policy.rb

@@ -0,0 +1,15 @@
+class ProtectedBranchPolicy < BasePolicy
+  delegate { @subject.project }
+
+  condition(:requires_admin_to_unprotect?, scope: :subject) do
+    @subject.name == 'master' && Gitlab::CurrentSettings.only_admins_can_unprotect_master_branch?
+  end
+
+  rule { can?(:admin_project) }.policy do
+    enable :update_protected_branch
+  end
+
+  rule { requires_admin_to_unprotect? & ~admin }.policy do
+    prevent :update_protected_branch
+  end
+end

app/services/protected_branches/update_service.rb

@@ -1,7 +1,7 @@
 module ProtectedBranches
   class UpdateService < BaseService
     def execute(protected_branch)
-      raise Gitlab::Access::AccessDeniedError unless can?(current_user, :admin_project, project)
+      raise Gitlab::Access::AccessDeniedError unless can?(current_user, :update_protected_branch, protected_branch)
 
       protected_branch.update(params)
       protected_branch

spec/policies/protected_branch_policy_spec.rb

@@ -0,0 +1,60 @@
+require 'spec_helper'
+
+describe ProtectedBranchPolicy do
+  let(:user) { create(:user) }
+  let(:name) { 'feature' }
+  let(:protected_branch) { create(:protected_branch, name: name) }
+  let(:project) { protected_branch.project }
+
+  subject { described_class.new(user, protected_branch) }
+
+  context 'when unprotection restriction feature is disabled' do
+    it "branches can't be updated by guests" do
+      project.add_guest(user)
+
+      is_expected.to be_disallowed(:update_protected_branch)
+    end
+
+    it 'branches can be updated via access to project settings' do
+      project.add_master(user)
+
+      is_expected.to be_allowed(:update_protected_branch)
+    end
+  end
+
+  context 'when unprotection restriction feature is enabled' do
+    before do
+      # stub_licensed_features(unprotection_restrictions: true)
+    end
+
+    context 'and unprotection is limited to admins' do #TODO: remove this is temporary exploration
+      before do
+        stub_ee_application_setting(only_admins_can_unprotect_master_branch: true)
+      end
+
+      context 'and the protection is for master' do
+        let(:name) { 'master' }
+
+        it 'project owners cannot remove protections' do
+          project.add_master(user)
+
+          is_expected.not_to be_allowed(:update_protected_branch)
+        end
+
+        it 'admins can remove protections' do
+          user.update!(admin: true)
+
+          is_expected.to be_allowed(:update_protected_branch)
+        end
+      end
+
+      context "and the protection isn't for master" do
+        it 'project owners can remove protections' do
+          project.add_master(user)
+
+          is_expected.to be_allowed(:update_protected_branch)
+        end
+      end
+    end
+  end
+end