diff --git a/app/controllers/tag_aliases_controller.rb b/app/controllers/tag_aliases_controller.rb
index 6baf30a5e..a677ec049 100644
--- a/app/controllers/tag_aliases_controller.rb
+++ b/app/controllers/tag_aliases_controller.rb
@@ -15,7 +15,7 @@ class TagAliasesController < ApplicationController
 
   def destroy
     @tag_alias = authorize TagAlias.find(params[:id])
-    @tag_alias.reject!
+    @tag_alias.reject!(CurrentUser.user)
 
     respond_with(@tag_alias, location: tag_aliases_path, notice: "Tag alias was deleted")
   end
diff --git a/app/controllers/tag_implications_controller.rb b/app/controllers/tag_implications_controller.rb
index 02264b92a..306cfff46 100644
--- a/app/controllers/tag_implications_controller.rb
+++ b/app/controllers/tag_implications_controller.rb
@@ -15,7 +15,7 @@ class TagImplicationsController < ApplicationController
 
   def destroy
     @tag_implication = authorize TagImplication.find(params[:id])
-    @tag_implication.reject!
+    @tag_implication.reject!(CurrentUser.user)
 
     respond_with(@tag_implication, location: tag_implications_path, notice: "Tag implication was deleted")
   end
diff --git a/app/logical/bulk_update_request_processor.rb b/app/logical/bulk_update_request_processor.rb
index 40d558919..65895d06c 100644
--- a/app/logical/bulk_update_request_processor.rb
+++ b/app/logical/bulk_update_request_processor.rb
@@ -144,11 +144,11 @@ class BulkUpdateRequestProcessor
 
         when :remove_alias
           tag_alias = TagAlias.active.find_by!(antecedent_name: args[0], consequent_name: args[1])
-          tag_alias.reject!
+          tag_alias.reject!(User.system)
 
         when :remove_implication
           tag_implication = TagImplication.active.find_by!(antecedent_name: args[0], consequent_name: args[1])
-          tag_implication.reject!
+          tag_implication.reject!(User.system)
 
         when :mass_update
           TagBatchChangeJob.perform_later(args[0], args[1])
@@ -157,7 +157,7 @@ class BulkUpdateRequestProcessor
           # Reject existing implications from any other tag to the one we're nuking
           # otherwise the tag won't be removed from posts that have those other tags
           if PostQueryBuilder.new(args[0]).is_simple_tag?
-            TagImplication.active.where(consequent_name: args[0]).each(&:reject!)
+            TagImplication.active.where(consequent_name: args[0]).each { |ti| ti.reject!(User.system) }
           end
 
           TagBatchChangeJob.perform_later(args[0], "-#{args[0]}")
diff --git a/app/models/mod_action.rb b/app/models/mod_action.rb
index 1796b0c97..393a75b2b 100644
--- a/app/models/mod_action.rb
+++ b/app/models/mod_action.rb
@@ -46,8 +46,10 @@ class ModAction < ApplicationRecord
     forum_post_delete: 102,
     tag_alias_create: 120,
     tag_alias_update: 121, # XXX unused
+    tag_alias_delete: 122,
     tag_implication_create: 140,
     tag_implication_update: 141, # XXX unused
+    tag_implication_delete: 142,
     ip_ban_create: 160,
     ip_ban_delete: 162,
     ip_ban_undelete: 163,
diff --git a/app/models/tag_alias.rb b/app/models/tag_alias.rb
index bc0dde4f5..1afdb43ac 100644
--- a/app/models/tag_alias.rb
+++ b/app/models/tag_alias.rb
@@ -43,6 +43,6 @@ class TagAlias < TagRelationship
     tag_relationships << TagAlias.active.find_by(antecedent_name: consequent_name, consequent_name: antecedent_name)
     tag_relationships << TagImplication.active.find_by(antecedent_name: antecedent_name, consequent_name: consequent_name)
     tag_relationships << TagImplication.active.find_by(antecedent_name: consequent_name, consequent_name: antecedent_name)
-    tag_relationships.each { |rel| rel.reject! if rel.present? }
+    tag_relationships.each { |rel| rel.reject!(User.system) if rel.present? }
   end
 end
diff --git a/app/models/tag_relationship.rb b/app/models/tag_relationship.rb
index 316ad3ac8..60010a5a7 100644
--- a/app/models/tag_relationship.rb
+++ b/app/models/tag_relationship.rb
@@ -43,8 +43,16 @@ class TagRelationship < ApplicationRecord
     status == "active"
   end
 
-  def reject!
+  # Mark an alias or implication as deleted, and log a mod action if the
+  # deletion was manually performed by an admin, as opposed to automatically by
+  # DanbooruBot as part of a BUR.
+  def reject!(rejector = CurrentUser.user)
     update!(status: "deleted")
+
+    if rejector != User.system
+      category = relationship == "tag alias" ? :tag_alias_delete : :tag_implication_delete
+      ModAction.log("deleted #{relationship} #{antecedent_name} -> #{consequent_name}", category, rejector)
+    end
   end
 
   module SearchMethods
diff --git a/test/functional/tag_aliases_controller_test.rb b/test/functional/tag_aliases_controller_test.rb
index 2db17a743..b0a38b08a 100644
--- a/test/functional/tag_aliases_controller_test.rb
+++ b/test/functional/tag_aliases_controller_test.rb
@@ -55,10 +55,12 @@ class TagAliasesControllerTest < ActionDispatch::IntegrationTest
 
     context "destroy action" do
       should "allow admins to delete aliases" do
-        delete_auth tag_alias_path(@tag_alias), create(:admin_user)
+        user = create(:admin_user)
+        delete_auth tag_alias_path(@tag_alias), user
 
         assert_response :redirect
         assert_equal("deleted", @tag_alias.reload.status)
+        assert_equal(user, ModAction.tag_alias_delete.last.creator)
       end
 
       should "not allow members to delete aliases" do
diff --git a/test/functional/tag_implications_controller_test.rb b/test/functional/tag_implications_controller_test.rb
index e7355b422..50948340b 100644
--- a/test/functional/tag_implications_controller_test.rb
+++ b/test/functional/tag_implications_controller_test.rb
@@ -65,10 +65,12 @@ class TagImplicationsControllerTest < ActionDispatch::IntegrationTest
 
     context "destroy action" do
       should "allow admins to delete implications" do
-        delete_auth tag_implication_path(@tag_implication), create(:admin_user)
+        user = create(:admin_user)
+        delete_auth tag_implication_path(@tag_implication), user
 
         assert_response :redirect
         assert_equal("deleted", @tag_implication.reload.status)
+        assert_equal(user, ModAction.tag_implication_delete.last.creator)
       end
 
       should "not allow members to delete aliases" do