When Tommy was a bit younger one time, I was about to put the dogs to bed and he was curled up by the couch in the living room. I called him to go to bed, and he just laid there looking at me. I went over and reached for his collar and he jerked his head away suddenly and growled, but did not bare his teeth or snap. Then he immediately leaped to his feet and dropped into a play bow, and then ran crazily around the living room a couple times in his hyper playful way before barreling on down the hall and into his bed where he knew was what I wanted. I was puzzled by this, as his behavior did seem somewhat defiant, but then also like he wanted to make a game of it. I since learned it always makes him nervous when someone grabs for his collar, and as I know he had been abused before he came here, I'm guessing he may have been dragged around by the collar as a pup too, I know of a certainty by the time he was 6 months old and the owners were getting rid of him, he lived on the end of a chain.

Anyway, was the growl real? To me it seemed like the same kind of response as a dog who yawns when nervous or uncertain. He jumped into an "I'm playing what a fun game!" mode but then did run off to his bed too. Afterwards, I worked with him more on come, go to bed, stay and so on, focusing on rewarding him when he did what I wanted. He's quite eager to please and loves food and praise reward so it was pretty easy. He loves to find treasures and carry them in his mouth but through time I taught him he got praise and reward when he came to me with things and gave them to me, so now when he finds things, he almost always comes to me and gives it to me rather than going off to hide with it.

I'd agree that working with Major on leave it, drop it, give it, etc. would probably be a good thing and would curb any possessive aggression that might develop. I do feel that when a dog shows defiance it is best not to get angry and disciplinary as this can spark a battle of dominance. Withdrawing attention and goodies and then rewarding them to him when he behaves properly is probably going to get the best results. Good luck.