There has got to be something in these Greenies that has never been used before in a chew toy.
I'm just waiting for a newsbreaking story announcing something like:
Overseas drug ring busted for producing Greenies, causing millions of canines to revert to primal Resource Guarding.
When the last Greenie got down to a risky size, it got tossed.
We would let Bodhi have it for 10 minute sessions a couple of times a week, wrapping it in a paper towel in between.
Bodhi went bonkers when he smelled the paper towel that my husband was going to throw away.
So, here's my new trick. I put a Greenie in a plastic container of Bodhi's regular dog food to use as treats. This way, I don't have to get his tummy accustomed to yet another food.
(He already has Pupcorn and the Natural Balance sausage on his treat repertoire).
Ever since Bodhi made it difficult to take the Greenie away, I constantly pick up his treats and return them to him, so that he knows that it's a gift from me and that I have a right to take it away.
In a fun way of course! 
The instructor of the Puppy Manners class we'll be going to has posted this article on her website:
http://doggiezen.com/handouts/resource-guarding.html