This behaviour can really escalate if you dont fix the problem quickly. People think that by taking away, then giving back toys/food/bones, you are teaching the dog that it's fine, he'll get it back, but infact, quite the opposite. Dogs live in the moment, all you're teaching the dog is that you will give him something, then, without warning, take it away!!! Totally unfair in his mind.
Basically, you need to teach him to trade. Start with a low value item (I'm going to use LVI from now on), something he is totally not possessive over, and a very high value food treat (HVFT), like bits of hot dog, or cooked chicken or liver. give him the LVI, wait a bit, then reach out with a hand offering him the HVFT, hold it a couple of steps away from the LVI, so he has to step away from it, let him have the HVFT and simultaneously take the LVI. once you have the LVI, give him a second HVFT then give back the LVI. Once you have the behaviour comfortable, up the anti a bit, give him a higher value LVI. Keep upping the anti over several days or weeks, till you are eventually trading him for the items he has prev. reacted over. By this time, the trade game is fun for him and he will have no qualms with people taking something from him, as long as he get's "paid for it"
Here's an analogy I love. If I gave you a $50 bill and walked away, but suddenly walked back and snatched it away from you, what would you do next time? you'd try to hide it, or get away so I cant take it. If I still managed to snatch it away, next time, you might yell at me. If I got it again, the next time you might slap at my hands. You would certainly develop deep suspicions every time I come near you when you have that $50 bill. But say, instead of snatching the $50 bill, I instead handed you a $100 bill, wouldn't you want me trading you as often as possible? Works the same with dogs.
There is a book called "MINE!" by Jean Donaldson that is all about resource guarding. I have not read it, but I've heard really good things about it.
I rehabbed Boo's severe resource guarding/food aggression in 4 weeks after I adopted him at 6.5 years old. He would attack me if I went anywhere near the kitchen where he was eating. I hand fed him, making him work for every piece of food. Sit, target hand, down, spin, and shy were all trained during that first 2 weeks. Then on the third week, I put his food dish on the floor between us, empty, and put one piece of food in at a time, waiting for him to look up before and asking for a sit or a down before dropping in the piece. I slowly increased how much food I was putting in at a time throughout that week, until he was getting the full amount. The last week, I gave him the full amount, but put small pieces of freeze dried liver in the bowl as he was eating, so he learned that my hand near/in the bowl is a very good thing. It worked brilliantly, and now, if I go near his dish he happily looks for me to put something really good in his dish (which I still do now and then) But I have NEVER taken anything away from him, and never will, unless it's a severe emergency, and even then I'll get him something he really wants (after the fact if I have to, but preferably beforehand)
My sister has a terrier that started behaving exactly the same as your dog is, over Pigs ears... I gave her the same advice, she followed through and now he has no issues with them near his beloved Pigs Ears LOL
