Train to Only Take Food From Me... Or if I "ok"...

I think that if you are serious about this, that it makes more sense to train him simply to not ever take treats or offerings from anyone else... it is more clear and more fair to make an absolute rule about this. He should be heavily rewarded by you with better than he was not allowed to have from the other person. However you choose to go about this, unless you intend for him to function as a guard or your circumstances make someone trying to harm him a high risk, you want to be very careful to not cause him to view people negatively or with suspicion... other people should not be allowed to predict that a correction will be forthcoming.

Fifty-some years ago in downtown Columbus, Ohio, folks came to work in their office building, and noticed two Dobermans sitting on the sidewalk in front of the building. When folks came out to go to lunch, the dogs were sitting there still. Someone was called, and the process of trying to catch the dogs began... they would move out of reach, and try to resume their stays... move and stay, move and stay, around and around the block... not wanting to break their commands, and not wanting to be caught. Eventually, they were caught. After some days of not eating, whoever had them began force-feeding them... whether they had a command to eat or had been taught to take food only from their owner, no one ever knew. It was a long time ago and I was a kid and I don't think I ever did know the end of the story. I do remember that it was never known how those dogs came to be there or what had happened to their owner.

Be careful what you train for.

I did this (sort of ) with my mastiff, Bella.

I did teach her to eat from a few other people, in case I am ever unable to be there (death, illness etc)

I would sneak visitors a treat, and give a sharp verbal correction when she tried to take it. I also did the same about things laying around by putting tasty treats around the farm and giving the same sharp verbal correction when she tried to take them.

I live in a rural area, people put out rat poison, and I was terrified that she would eat a poisoned rat. I also had a foster Pitbull get poisoned by some crappy neighbors, I am a little paranoid.

She knows (and obeys) not to eat anything that is not in MY hand or in HER bowl (which stays IN my house).

The trick is to ALWAYS follow up that sharp correction with a treat from your hand and lots of praise when she takes it. She needs to understand that she is not being corrected for eating, that she is being corrected from eating from someone else's hand.

She also needs to have a solid understanding of "NO" and "leave it" BEFORE you start this.

I personally would go with a release word and teach that. I have had neighbors watch my dogs and forgot to give them the release until the second day when he said they would not eat. I totally forgot to tell them how to feed them, just took it for granted since it was habit for us. Ours is easy, "okay", but it can be anything if you want to pick something that people may not guess, like snoozerdoddle or something else only you and the people you wanted to know. Honestly this is one of the easiest things to teach ever because the sole purpose is for them to get fed. I even do this with my visiting dogs and they catch on usually after the first meal. With my own dogs you advance the command and we have fun doing it. Okay, we have fun, maybe not the dogs. We'll say silly words, like rainbow, fish, moster, bellybutton, totay, motay, rotay, for example while the dogs wait for their word "okay". Play leave it games, make them work for their food. Even their treats, leave the treats and correct them if they go after it without the release. You may have to start by covering the treat with your hand if they go after it but typically within the first lesson they will start to understand if you give a verbal ah-ah, then when you release them with their special word, encourage them to get the treat, and give lots of praises. (This was one of my grandmothers favorite games to play with J when we would go visit her) The dogs never fail to get really excited too when you say their special word.