I have seen in so many place where they would have mentioned "You may not.." etc for the things people shouldn't do. For eg: in companies where USB is not allowed, they will mention like this "You may not use USB/CD etc", similarly "You may not download free softwares", "You may not tailgate the doors" etc.
These all things should be like this right "You should not use USB/CD etc", "You should not download free softwares" etc, this "May not" seems like saying "optional" it may indicate like "people may follow" etc
Can anyone guide me in this? I always get confuse in this.