new file mode 100644
--- /dev/null
+++ b/hghooks/mozhghooks/check/prevent_ftl_changes.py
@@ -0,0 +1,66 @@
+# This software may be used and distributed according to the terms of the
+# GNU General Public License version 2 or any later version.
+
+from __future__ import absolute_import
+from mozautomation.commitparser import (
+    parse_requal_reviewers,
+)
+
+from ..checks import (
+    PreTxnChangegroupCheck,
+    print_banner,
+)
+
+FTL_DRIVERS = [
+    ("Francesco Lodolo", "flod"),
+    ("Zibi Braniecki", "gandalf"),
+    ("Axel Hecht", "pike"),
+    ("Stas Malolepszy", "stas")
+]
+
+
+FTL_COMMIT_FOUND = """
+You are trying to commit a change to an FTL file.
+At the moment modifying FTL files requires a review from
+one of the L10n Drivers.
+Please, request review from either:
+"""
+
+for (name, nick) in FTL_DRIVERS:
+    FTL_COMMIT_FOUND += "    - {} (:{})\n".format(name, nick)
+
+
+class FTLCheck(PreTxnChangegroupCheck):
+    """Prevents FTL file modifications without appropriate review.
+
+    FTL is a new localization format currently being introduced
+    into Gecko and Firefox.
+    During the initial period we keep tight control over new
+    FTL strings being added to the repository.
+
+    In this period, we require that one of the L10n Drivers
+    reviews every commit that touched an FTL file.
+    """
+    @property
+    def name(self):
+        return 'ftl_check'
+
+    def relevant(self):
+        return self.repo_metadata['firefox_releasing']
+
+    def pre(self):
+        pass
+
+    def check(self, ctx):
+        if any(f.endswith('.ftl') for f in ctx.files()):
+            requal = parse_requal_reviewers(ctx.description())
+            reviewers = [nick for (name, nick) in FTL_DRIVERS]
+            if any(nick in reviewers for nick in requal):
+                return True
+
+            print_banner(self.ui, 'error', FTL_COMMIT_FOUND)
+            return False
+        return True
+
+    def post_check(self):
+        return True

--- a/hghooks/mozhghooks/extension.py
+++ b/hghooks/mozhghooks/extension.py
@@ -15,26 +15,28 @@ buglink = 'https://bugzilla.mozilla.org/
 
 
 def get_check_classes(hook):
     # TODO come up with a mechanism for automatically discovering checks
     # so we don't have to enumerate them all.
     from mozhghooks.check import (
         advertise_upgrade,
         prevent_cross_channel_messages,
+        prevent_ftl_changes,
         prevent_subrepos,
         prevent_symlinks,
         single_root,
         try_task_config_file,
     )
 
     # TODO check to hook mapping should also be automatically discovered.
     if hook == 'pretxnchangegroup':
         return (
             prevent_cross_channel_messages.XChannelMessageCheck,
+            prevent_ftl_changes.FTLCheck,
             prevent_subrepos.PreventSubReposCheck,
             prevent_symlinks.PreventSymlinksCheck,
             single_root.SingleRootCheck,
             try_task_config_file.TryConfigCheck,
         )
 
     elif hook == 'changegroup':
         return (

new file mode 100644
--- /dev/null
+++ b/hghooks/tests/test-prevent-ftl-changes.t
@@ -0,0 +1,58 @@
+  $ . $TESTDIR/hghooks/tests/common.sh
+
+Commit adding an FTL file without appropriate reviewer errors
+
+  $ hg init normal
+  $ configurehooks normal
+  $ touch normal/.hg/IS_FIREFOX_REPO
+  $ hg -q clone normal client-normal
+  $ cd client-normal
+  $ touch test.ftl
+  $ hg -q commit -A -m 'add test.ftl'
+  $ hg push
+  pushing to $TESTTMP/normal
+  searching for changes
+  adding changesets
+  adding manifests
+  adding file changes
+  added 1 changesets with 1 changes to 1 files
+  
+  ************************ ERROR *************************
+  You are trying to commit a change to an FTL file.
+  At the moment modifying FTL files requires a review from
+  one of the L10n Drivers.
+  Please, request review from either:
+      - Francesco Lodolo (:flod)
+      - Zibi Braniecki (:gandalf)
+      - Axel Hecht (:pike)
+      - Stas Malolepszy (:stas)
+  ********************************************************
+  
+  transaction abort!
+  rollback completed
+  abort: pretxnchangegroup.mozhooks hook failed
+  [255]
+
+Commit adding an FTL file with appropriate reviewer works
+
+  $ hg commit --amend -m 'add test.ftl. r=flod'
+  saved backup bundle to $TESTTMP/client-normal/.hg/strip-backup/caf1d529f784-2085d403-amend-backup.hg (glob)
+  $ hg push
+  pushing to $TESTTMP/normal
+  searching for changes
+  adding changesets
+  adding manifests
+  adding file changes
+  added 1 changesets with 1 changes to 1 files
+
+Commit adding an FTL file with appropriate reviewer works
+
+  $ touch test2.ftl
+  $ hg -q commit -A -m 'add test2.ftl. r=someonelse,stas'
+  $ hg push
+  pushing to $TESTTMP/normal
+  searching for changes
+  adding changesets
+  adding manifests
+  adding file changes
+  added 1 changesets with 1 changes to 1 files