Originally Posted by irishguy28

I don't think that's what the OP is asking. He's either going to go through security as if he is a departing passenger (which will require a valid boarding pass) and then instead of boarding his flight will - for whatever reason (accompanying a child/nervous flyer to the gate?) - not board the flight and instead want to get back out landside; or he's in transit and - again for whatever reason - is not going to board his onward flight (hidden city ticketing, perhaps).

There is a way back landside from the departures area but it's not well advertised/signed. Just ask any employee and they will tell you how to get back landside.

(I've had to do this twice but I couldn't actually tell you how to find the "Exit")