Alternative training methods for 'counter cruisers'?

I have a Husky/Chow mix who's a 'counter cruiser'. I'm currently working with a trainer, and have been for over 8 weeks, but the problem is still strong. (Although he's made great improvement in other areas). We've tried using soda can's filled with pennies or pebbles, we've tried using small mouse traps, we've tried about 4 different brands of deterrent spray, (all under the guidance of the trainer). It doesn't stop him, in fact, I get the impression he considers them all a game. He doesn't counter cruise for just food either, (which I make sure not to leave out), he'll grab just about anything, then run outside with it trying to get us to chase him. (which I don't, to keep from encouraging the behavior, I simply wait for him to come close then grab him and take the item from his mouth). He gets a 45 to 60 minute walk in the mornings, and he spends an hour at the dog park twice a week. Anyone know of any alternative training methods I might try to deter this behavior? He's an otherwise good dog.