Use hook_menu_alter to change access callbacks I'm trying to working with hook_menu_alter, I'm tryng to change, for example, access callback to an admin path (admin/config/account/people/fields).

I've create a permission and I've added to a role.
Now I'm trying this:

function mymodule_menu_alter(&amp;$items) {
   $items['admin/config/people/account/fields']['access arguments'] = array('my custom permission');  
}


But it doesn't work.

Can I edit this "system" modules permissions?
Your code is correct (that's definitely the way to override the access arguments for a path using hook_menu_alter()).

If it's not working you just need to clear your caches (and of course make sure that your custom module is installed and enabled).

I just copied your code into a test site, cleared the caches, and no longer receive 403 errors when visiting that page as an anonymous user.