diff --git a/mobile/android/.eslintrc.js b/mobile/android/.eslintrc.js
index 2db1a54294ed..e64585fff32c 100644
--- a/mobile/android/.eslintrc.js
+++ b/mobile/android/.eslintrc.js
@@ -1,14 +1,6 @@
 "use strict";
 
 module.exports = {
-  rules: {
-    // Rules enabled in mozilla/recommended, and disabled for now, we should
-    // re-enable these over time.
-    "consistent-return": "off",
-    "no-empty": "off",
-    "no-redeclare": "off",
-  },
-
   "overrides": [{
     files: [
       // Bug 1425048 - mainly going away, see bug 1583370.
diff --git a/mobile/android/actors/LoadURIDelegateChild.jsm b/mobile/android/actors/LoadURIDelegateChild.jsm
index bf0c0171884a..e6b482fb808a 100644
--- a/mobile/android/actors/LoadURIDelegateChild.jsm
+++ b/mobile/android/actors/LoadURIDelegateChild.jsm
@@ -51,7 +51,7 @@ class LoadURIDelegateChild extends GeckoViewActorChild {
     if (!this.isContentWindow) {
       debug`loadURI: not a content window`;
       // This is an internal Gecko window, nothing to do
-      return;
+      return false;
     }
 
     return LoadURIDelegate.load(
@@ -72,7 +72,7 @@ class LoadURIDelegateChild extends GeckoViewActorChild {
     if (!this.isContentWindow) {
       // This is an internal Gecko window, nothing to do
       debug`handleLoadError: not a content window`;
-      return;
+      return null;
     }
 
     if (aUri && LoadURIDelegate.isSafeBrowsingError(aError)) {
diff --git a/mobile/android/components/extensions/ext-utils.js b/mobile/android/components/extensions/ext-utils.js
index c07d2f898743..d8d42f5ea2cf 100644
--- a/mobile/android/components/extensions/ext-utils.js
+++ b/mobile/android/components/extensions/ext-utils.js
@@ -14,7 +14,6 @@ ChromeUtils.defineModuleGetter(
   "resource://gre/modules/GeckoViewTab.jsm"
 );
 
-/* globals EventDispatcher */
 var { EventDispatcher } = ChromeUtils.import(
   "resource://gre/modules/Messaging.jsm"
 );
diff --git a/mobile/android/components/geckoview/GeckoViewPermission.js b/mobile/android/components/geckoview/GeckoViewPermission.js
index ebe4910f72e7..695d661b0d57 100644
--- a/mobile/android/components/geckoview/GeckoViewPermission.js
+++ b/mobile/android/components/geckoview/GeckoViewPermission.js
@@ -116,7 +116,7 @@ GeckoViewPermission.prototype = {
     })
       .then(devices => {
         if (win.closed) {
-          return;
+          return Promise.resolve();
         }
 
         let sources = devices.map(device => {
diff --git a/mobile/android/components/geckoview/GeckoViewPrompt.js b/mobile/android/components/geckoview/GeckoViewPrompt.js
index 0f530d783813..de1684ae1f6e 100644
--- a/mobile/android/components/geckoview/GeckoViewPrompt.js
+++ b/mobile/android/components/geckoview/GeckoViewPrompt.js
@@ -484,7 +484,7 @@ PromptDelegate.prototype = {
   _showPrompt(aMsg) {
     let result = undefined;
     if (!this._domWin || !this._changeModalState(/* aEntering */ true)) {
-      return;
+      return result;
     }
     try {
       this.asyncShowPrompt(aMsg, res => (result = res));
diff --git a/mobile/android/geckoview/src/androidTest/assets/www/hungScript.html b/mobile/android/geckoview/src/androidTest/assets/www/hungScript.html
index 8595725df149..695ff5392e94 100644
--- a/mobile/android/geckoview/src/androidTest/assets/www/hungScript.html
+++ b/mobile/android/geckoview/src/androidTest/assets/www/hungScript.html
@@ -5,7 +5,8 @@
 	<script>
 		var start = new Date().getTime();
 		document.getElementById("content").innerHTML = "Started";
+		// eslint-disable-next-line no-empty
 		while((new Date().getTime() - start) < 5000 ) {};
 		document.getElementById("content").innerHTML = "Finished";
 	</script>
-</html>
\ No newline at end of file
+</html>
diff --git a/mobile/android/modules/geckoview/GeckoViewMedia.jsm b/mobile/android/modules/geckoview/GeckoViewMedia.jsm
index bfdc34cbd8f7..02ebe879cdd1 100644
--- a/mobile/android/modules/geckoview/GeckoViewMedia.jsm
+++ b/mobile/android/modules/geckoview/GeckoViewMedia.jsm
@@ -81,6 +81,8 @@ const GeckoViewRecordingMedia = {
             return STATUS_RECORDING;
           case MediaManagerService.STATE_NOCAPTURE:
             return STATUS_INACTIVE;
+          default:
+            throw new Error("Unexpected activityStatus value");
         }
       };
 
diff --git a/mobile/android/modules/geckoview/GeckoViewUtils.jsm b/mobile/android/modules/geckoview/GeckoViewUtils.jsm
index e91c77024ad2..82b6e3b4cc45 100644
--- a/mobile/android/modules/geckoview/GeckoViewUtils.jsm
+++ b/mobile/android/modules/geckoview/GeckoViewUtils.jsm
@@ -482,7 +482,7 @@ var GeckoViewUtils = {
       }
     }
 
-    return aLogger[aLevel.toLowerCase()](strs, ...aExprs);
+    aLogger[aLevel.toLowerCase()](strs, ...aExprs);
   },
 };
 
diff --git a/mobile/android/tests/browser/chrome/test_android_log.html b/mobile/android/tests/browser/chrome/test_android_log.html
index b1cd6ac14910..70dcac433309 100644
--- a/mobile/android/tests/browser/chrome/test_android_log.html
+++ b/mobile/android/tests/browser/chrome/test_android_log.html
@@ -12,8 +12,6 @@ Migrated from Robocop: https://bugzilla.mozilla.org/show_bug.cgi?id=1184186
   <link rel="stylesheet" type="text/css" href="chrome://mochikit/content/tests/SimpleTest/test.css"/>
   <script type="application/javascript">
 
-  /* globals AndroidLog */
-
   const TAG = "AndroidLogTest";
 
   const VERBOSE_MESSAGE = "This is a verbose message.";
diff --git a/mobile/android/tests/browser/chrome/test_resource_substitutions.html b/mobile/android/tests/browser/chrome/test_resource_substitutions.html
index 2a4c21e1febb..7d8c5d4b9569 100644
--- a/mobile/android/tests/browser/chrome/test_resource_substitutions.html
+++ b/mobile/android/tests/browser/chrome/test_resource_substitutions.html
@@ -12,9 +12,9 @@ Migrated from Robocop: https://bugzilla.mozilla.org/show_bug.cgi?id=1184186
   <link rel="stylesheet" type="text/css" href="chrome://mochikit/content/tests/SimpleTest/test.css"/>
   <script type="application/javascript">
 
-  const {Promise} = ChromeUtils.import("resource://gre/modules/Promise.jsm"); /* global Promise */
-  const {Services} = ChromeUtils.import("resource://gre/modules/Services.jsm"); /* global Services */
-  const {NetUtil} = ChromeUtils.import("resource://gre/modules/NetUtil.jsm"); /* global NetUtil */
+  const {Promise} = ChromeUtils.import("resource://gre/modules/Promise.jsm");
+  const {Services} = ChromeUtils.import("resource://gre/modules/Services.jsm");
+  const {NetUtil} = ChromeUtils.import("resource://gre/modules/NetUtil.jsm");
 
   function readChannel(url) {
     let deferred = Promise.defer();
diff --git a/mobile/android/tests/browser/chrome/test_simple_discovery.html b/mobile/android/tests/browser/chrome/test_simple_discovery.html
index ff262bc5635b..97cac761557e 100644
--- a/mobile/android/tests/browser/chrome/test_simple_discovery.html
+++ b/mobile/android/tests/browser/chrome/test_simple_discovery.html
@@ -14,8 +14,6 @@ Migrated from Robocop: https://bugzilla.mozilla.org/show_bug.cgi?id=1184186
 
   "use strict";
 
-  /* globals SimpleServiceDiscovery */
-
   const {Services} = ChromeUtils.import("resource://gre/modules/Services.jsm");
   const {SimpleServiceDiscovery} = ChromeUtils.import("resource://gre/modules/SimpleServiceDiscovery.jsm");
 
diff --git a/mobile/android/tests/browser/chrome/test_video_discovery.html b/mobile/android/tests/browser/chrome/test_video_discovery.html
index c7cd3c0b8c7b..cb4636bd20e7 100644
--- a/mobile/android/tests/browser/chrome/test_video_discovery.html
+++ b/mobile/android/tests/browser/chrome/test_video_discovery.html
@@ -14,8 +14,6 @@ Migrated from Robocop: https://bugzilla.mozilla.org/show_bug.cgi?id=1184186
 
   "use strict";
 
-  /* globals SimpleServiceDiscovery */
-
   const {Services} = ChromeUtils.import("resource://gre/modules/Services.jsm");
   const {SimpleServiceDiscovery} = ChromeUtils.import("resource://gre/modules/SimpleServiceDiscovery.jsm");