diff --git a/public/src/admin/manage/admins-mods.js b/public/src/admin/manage/admins-mods.js
index 4aa3bfceee8d..f2b3cea6e69f 100644
--- a/public/src/admin/manage/admins-mods.js
+++ b/public/src/admin/manage/admins-mods.js
@@ -63,16 +63,13 @@ define('admin/manage/admins-mods', ['translator', 'benchpress', 'autocomplete',
 
 			bootbox.confirm('[[admin/manage/users:alerts.confirm-remove-global-mod]]', function (confirm) {
 				if (confirm) {
-					socket.emit('admin.groups.leave', { uid: uid, groupName: 'Global Moderators' }, function (err) {
-						if (err) {
-							return app.alertError(err.message);
-						}
+					api.del('/groups/global-moderators/membership/' + uid, undefined, () => {
 						app.alertSuccess('[[admin/manage/users:alerts.remove-global-mod-success]]');
 						userCard.remove();
 						if (!$('.global-moderator-area').children().length) {
 							$('#no-global-mods-warning').removeClass('hidden');
 						}
-					});
+					}, err => app.alertError(err.status.message));
 				}
 			});
 		});
diff --git a/public/src/admin/manage/group.js b/public/src/admin/manage/group.js
index 3a31f89c6318..4cfef7eeaa72 100644
--- a/public/src/admin/manage/group.js
+++ b/public/src/admin/manage/group.js
@@ -1,6 +1,5 @@
 'use strict';
 
-
 define('admin/manage/group', [
 	'forum/groups/memberlist',
 	'iconSelect',
@@ -8,7 +7,8 @@ define('admin/manage/group', [
 	'translator',
 	'categorySelector',
 	'groupSearch',
-], function (memberList, iconSelect, colorpicker, translator, categorySelector, groupSearch) {
+	'api',
+], function (memberList, iconSelect, colorpicker, translator, categorySelector, groupSearch, api) {
 	var Groups = {};
 
 	Groups.init = function () {
@@ -137,15 +137,9 @@ define('admin/manage/group', [
 						if (!confirm) {
 							return;
 						}
-						socket.emit('admin.groups.leave', {
-							uid: uid,
-							groupName: groupName,
-						}, function (err) {
-							if (err) {
-								return app.alertError(err.message);
-							}
+						api.del('/groups/' + ajaxify.data.group.slug + '/membership/' + uid, undefined, () => {
 							userRow.slideUp().remove();
-						});
+						}, err => app.alertError(err.status.message));
 					});
 					break;
 				default:
diff --git a/public/src/admin/manage/users.js b/public/src/admin/manage/users.js
index 64a1ee8c96e6..858ffdadab5f 100644
--- a/public/src/admin/manage/users.js
+++ b/public/src/admin/manage/users.js
@@ -108,12 +108,9 @@ define('admin/manage/users', ['translator', 'benchpress', 'autocomplete', 'api']
 						var groupCard = $(this).parents('[data-group-name]');
 						var groupName = groupCard.attr('data-group-name');
 						var uid = $(this).parents('[data-uid]').attr('data-uid');
-						socket.emit('admin.groups.leave', { uid: uid, groupName: groupName }, function (err) {
-							if (err) {
-								return app.alertError(err);
-							}
+						api.del('/groups/' + utils.slugify(groupName) + '/membership/' + uid, undefined, () => {
 							groupCard.remove();
-						});
+						}, err => app.alertError(err.status.message));
 						return false;
 					});
 				});
diff --git a/public/src/client/groups/details.js b/public/src/client/groups/details.js
index ba2a0cb3e912..03db28e96f67 100644
--- a/public/src/client/groups/details.js
+++ b/public/src/client/groups/details.js
@@ -109,8 +109,11 @@ define('forum/groups/details', [
 					api.put('/groups/' + ajaxify.data.group.slug + '/membership/' + (uid || app.user.uid), undefined, () => ajaxify.refresh(), err => app.alertError(err.status.message));
 					break;
 
-				case 'leave':	// intentional fall-throughs!
-				case 'accept':
+				case 'leave':
+					api.del('/groups/' + ajaxify.data.group.slug + '/membership/' + (uid || app.user.uid), undefined, () => ajaxify.refresh(), err => app.alertError(err.status.message));
+					break;
+
+				case 'accept':	// intentional fall-throughs!
 				case 'reject':
 				case 'issueInvite':
 				case 'rescindInvite':
diff --git a/public/src/client/groups/memberlist.js b/public/src/client/groups/memberlist.js
index 615a3e8fce51..e0a3db3dd802 100644
--- a/public/src/client/groups/memberlist.js
+++ b/public/src/client/groups/memberlist.js
@@ -1,7 +1,6 @@
 'use strict';
 
-
-define('forum/groups/memberlist', function () {
+define('forum/groups/memberlist', ['api'], function (api) {
 	var MemberList = {};
 	var searchInterval;
 	var groupName;
@@ -83,7 +82,13 @@ define('forum/groups/memberlist', function () {
 		if (groupName === 'administrators') {
 			socket.emit('admin.user.makeAdmins', uids, done);
 		} else {
-			socket.emit('groups.addMember', { groupName: groupName, uid: uids }, done);
+			var requests = uids.map(function (uid) {
+				return api.put('/groups/' + ajaxify.data.group.slug + '/membership/' + uid);
+			});
+
+			$.when(requests)
+				.done(done)
+				.fail(err => app.alertError(err.status.message));
 		}
 	}
 
diff --git a/src/controllers/write/groups.js b/src/controllers/write/groups.js
index f04d17a3ce71..db48853bd6a8 100644
--- a/src/controllers/write/groups.js
+++ b/src/controllers/write/groups.js
@@ -1,9 +1,13 @@
 'use strict';
 
+const validator = require('validator');
+
 const user = require('../../user');
 const groups = require('../../groups');
 const events = require('../../events');
 const meta = require('../../meta');
+const utils = require('../../utils');
+const notifications = require('../../notifications');
 
 const helpers = require('../helpers');
 
@@ -85,6 +89,42 @@ Groups.join = async (req, res) => {
 	});
 };
 
+Groups.leave = async (req, res) => {
+	const [group, userExists] = await Promise.all([
+		groups.getByGroupslug(req.params.slug, {
+			uid: req.params.uid,
+		}),
+		user.exists(req.params.uid),
+	]);
+
+	if (!userExists) {
+		throw new Error('[[error:invalid-uid]]');
+	} else if (group.disableLeave) {
+		throw new Error('[[error:group-leave-disabled]]');
+	} else if (!group.isMember) {
+		// No change
+		return helpers.formatApiResponse(200, res);
+	}
+
+	await groups.leave(group.name, req.params.uid);
+
+	// Notify owners of user having left
+	const username = await user.getUserField(req.params.uid, 'username');
+	const notification = await notifications.create({
+		type: 'group-leave',
+		bodyShort: '[[groups:membership.leave.notification-title, ' + username + ', ' + group.name + ']]',
+		nid: 'group:' + validator.escape(group.name) + ':uid:' + req.params.uid + ':group-leave',
+		path: '/groups/' + utils.slugify(group.name),
+	});
+	const uids = await groups.getOwners(group.name);
+	await notifications.push(notification, uids);
+
+	helpers.formatApiResponse(200, res);
+	logGroupEvent(req, 'group-leave', {
+		groupName: group.name,
+	});
+};
+
 function logGroupEvent(req, event, additional) {
 	events.log({
 		type: event,
diff --git a/src/routes/write/groups.js b/src/routes/write/groups.js
index 474bc60f0952..275e0ec30283 100644
--- a/src/routes/write/groups.js
+++ b/src/routes/write/groups.js
@@ -13,36 +13,7 @@ module.exports = function () {
 	setupApiRoute(router, '/', middleware, [...middlewares, middleware.checkRequired.bind(null, ['name']), middleware.exposePrivilegeSet], 'post', controllers.write.groups.create);
 	setupApiRoute(router, '/:slug', middleware, [...middlewares, middleware.assertGroup, middleware.exposePrivileges], 'delete', controllers.write.groups.delete);
 	setupApiRoute(router, '/:slug/membership/:uid', middleware, [...middlewares, middleware.assertGroup, middleware.exposePrivileges], 'put', controllers.write.groups.join);
-
-	// app.put('/:slug/membership/:uid', middleware.exposeGroupName, apiMiddleware.validateGroup, apiMiddleware.requireUser, apiMiddleware.requireAdmin, function(req, res) {
-	// 	Groups.join(res.locals.groupName, req.params.uid, function(err) {
-	// 		errorHandler.handle(err, res);
-	// 	});
-	// });
-
-	// app.delete('/:slug/membership', apiMiddleware.requireUser, middleware.exposeGroupName, apiMiddleware.validateGroup, function(req, res) {
-	// 	Groups.isMember(req.user.uid, res.locals.groupName, function(err, isMember) {
-	// 		if (isMember) {
-	// 			Groups.leave(res.locals.groupName, req.user.uid, function(err) {
-	// 				errorHandler.handle(err, res);
-	// 			});
-	// 		} else {
-	// 			errorHandler.respond(400, res);
-	// 		}
-	// 	});
-	// });
-
-	// app.delete('/:slug/membership/:uid', middleware.exposeGroupName, apiMiddleware.validateGroup, apiMiddleware.requireUser, apiMiddleware.requireAdmin, function(req, res) {
-	//     Groups.isMember(req.params.uid, res.locals.groupName, function(err, isMember) {
-	//         if (isMember) {
-	//             Groups.leave(res.locals.groupName, req.params.uid, function(err) {
-	//                 errorHandler.handle(err, res);
-	//             });
-	//         } else {
-	//             errorHandler.respond(400, res);
-	//         }
-	//     });
-	// });
+	setupApiRoute(router, '/:slug/membership/:uid', middleware, [...middlewares, middleware.assertGroup, middleware.exposePrivileges], 'delete', controllers.write.groups.leave);
 
 	return router;
 };
diff --git a/src/socket.io/admin/groups.js b/src/socket.io/admin/groups.js
index e98bdf66a1ae..dc875ccfe81b 100644
--- a/src/socket.io/admin/groups.js
+++ b/src/socket.io/admin/groups.js
@@ -39,6 +39,8 @@ Groups.join = async (socket, data) => {
 };
 
 Groups.leave = async function (socket, data) {
+	sockets.warnDeprecated(socket, 'DELETE /api/v1/groups/:slug/membership/:uid');
+
 	if (!data) {
 		throw new Error('[[error:invalid-data]]');
 	}
diff --git a/src/socket.io/groups.js b/src/socket.io/groups.js
index 850e18435123..706b2b6b7fe9 100644
--- a/src/socket.io/groups.js
+++ b/src/socket.io/groups.js
@@ -69,6 +69,8 @@ SocketGroups.join = async (socket, data) => {
 };
 
 SocketGroups.leave = async (socket, data) => {
+	sockets.warnDeprecated(socket, 'DELETE /api/v1/groups/:slug/membership/:uid');
+
 	if (socket.uid <= 0) {
 		throw new Error('[[error:invalid-uid]]');
 	}