Leech protection can be enabled/disabled on a per-user basis. Is there any particular reason you wish to disable this functionality?
What you can do is disable Leech Protection from feature manager. This will stop new users from using it (unless they have sufficient knowledge of .htaccess to do this themselves). Unfortunately, this would also prevent users currently using this functionality from easily disabling this. So you may want to find the accounts using this, disable leech protection then disable this from feature manager to prevent users from using this.