diff --git a/app/models/tag.rb b/app/models/tag.rb
index b9f3ffdb8..eb13f5b64 100644
--- a/app/models/tag.rb
+++ b/app/models/tag.rb
@@ -1,6 +1,7 @@
 class Tag < ActiveRecord::Base
   METATAGS = "-user|user|-approver|approver|commenter|comm|noter|-pool|pool|-fav|fav|sub|md5|-rating|rating|-locked|locked|width|height|mpixels|score|favcount|filesize|source|-source|id|-id|date|age|order|-status|status|tagcount|gentags|arttags|chartags|copytags|parent|-parent|pixiv_id|pixiv"
-  attr_accessible :category
+  attr_accessible :category, :as => [:moderator, :janitor, :contributor, :gold, :member, :anonymous, :default, :builder, :admin]
+  attr_accessible :is_locked, :as => [:moderator, :janitor, :admin]
   has_one :wiki_page, :foreign_key => "name", :primary_key => "title"
 
   module ApiMethods
@@ -141,7 +142,7 @@ class Tag < ActiveRecord::Base
         if category
           category_id = categories.value_for(category)
 
-          if category_id != tag.category && (CurrentUser.is_builder? || tag.post_count <= 50)
+          if category_id != tag.category && !tag.is_locked? && (CurrentUser.is_builder? || tag.post_count <= 50)
             tag.update_column(:category, category_id)
             tag.update_category_cache_for_all
           end
diff --git a/app/views/tags/edit.html.erb b/app/views/tags/edit.html.erb
index f08fdf5a7..6ae686874 100644
--- a/app/views/tags/edit.html.erb
+++ b/app/views/tags/edit.html.erb
@@ -3,7 +3,14 @@
     <h1>Tag: <%= @tag.name %></h1>
 
     <%= simple_form_for(@tag) do |f| %>
-      <%= f.input :category, :collection => Danbooru.config.canonical_tag_category_mapping.to_a, :include_blank => false %>
+      <% unless @tag.is_locked? %>
+        <%= f.input :category, :collection => Danbooru.config.canonical_tag_category_mapping.to_a, :include_blank => false %>
+      <% end %>
+
+      <% if CurrentUser.user.is_janitor? %>
+        <%= f.input :is_locked, :collection => [["No", "false"], ["Yes", "true"]] %>
+      <% end %>
+
       <%= f.button :submit, "Submit" %>
     <% end %>
   </div>
diff --git a/db/migrate/20130620215658_add_is_locked_to_tags.rb b/db/migrate/20130620215658_add_is_locked_to_tags.rb
new file mode 100644
index 000000000..1d9575a15
--- /dev/null
+++ b/db/migrate/20130620215658_add_is_locked_to_tags.rb
@@ -0,0 +1,6 @@
+class AddIsLockedToTags < ActiveRecord::Migration
+  def change
+    execute "set statement_timeout = 0"
+    add_column :tags, :is_locked, :boolean, :null => false, :default => false
+  end
+end
diff --git a/db/structure.sql b/db/structure.sql
index 1bdcbd170..c6d301fe2 100644
--- a/db/structure.sql
+++ b/db/structure.sql
@@ -2488,7 +2488,8 @@ CREATE TABLE tags (
     related_tags text,
     related_tags_updated_at timestamp without time zone,
     created_at timestamp without time zone NOT NULL,
-    updated_at timestamp without time zone NOT NULL
+    updated_at timestamp without time zone NOT NULL,
+    is_locked boolean DEFAULT false NOT NULL
 );
 
 
@@ -6421,4 +6422,6 @@ INSERT INTO schema_migrations (version) VALUES ('20130506154136');
 
 INSERT INTO schema_migrations (version) VALUES ('20130606224559');
 
-INSERT INTO schema_migrations (version) VALUES ('20130618230158');
\ No newline at end of file
+INSERT INTO schema_migrations (version) VALUES ('20130618230158');
+
+INSERT INTO schema_migrations (version) VALUES ('20130620215658');
\ No newline at end of file
diff --git a/test/unit/tag_test.rb b/test/unit/tag_test.rb
index 63b7b775d..d6e9add27 100644
--- a/test/unit/tag_test.rb
+++ b/test/unit/tag_test.rb
@@ -84,6 +84,22 @@ class TagTest < ActiveSupport::TestCase
       MEMCACHE.flush_all
     end
 
+    should "be lockable by a janitor" do
+      @tag = FactoryGirl.create(:tag)
+      @tag.update_attributes({:is_locked => true}, :as => :janitor)
+      @tag.reload
+      assert_equal(true, @tag.is_locked?)
+    end
+
+    should "not be lockable by a user" do
+      @tag = FactoryGirl.create(:tag)
+      assert_raises(ActiveModel::MassAssignmentSecurity::Error) do
+        @tag.update_attributes({:is_locked => true}, :as => :member)
+      end
+      @tag.reload
+      assert_equal(false, @tag.is_locked?)
+    end
+
     should "know its category name" do
       @tag = FactoryGirl.create(:artist_tag)
       assert_equal("Artist", @tag.category_name)
@@ -153,6 +169,14 @@ class TagTest < ActiveSupport::TestCase
       end
     end
 
+    should "not change the category is the tag is locked" do
+      tag = FactoryGirl.create(:tag, :is_locked => true)
+      assert_equal(true, tag.is_locked?)
+      Tag.find_or_create_by_name("artist:#{tag.name}")
+      tag.reload
+      assert_equal(0, tag.category)
+    end
+
     should "be created when one doesn't exist" do
       assert_difference("Tag.count", 1) do
         tag = Tag.find_or_create_by_name("hoge")