We have a 5 and a half year old lab. He's very laid back and generally calm and well behaved, however he is a total stomach on legs and will eat everything if given the opportunity.
He will growl on the odd occasion - if told to go outside last thing at night he will sometimes growl at DH, but not at me as I use a firmer tone of voice.
A friend (experienced dog owner) walks him sometimes, when she told him to stop eating (probably poo) something last week (I have only just found out), he growled at her and bit her when told off. (Not a major bite but tooth did make a mark)
Where do I go from here? Is it normal for a dog to growl if told to do something that they don't want to do (to stop eating something or to go outside last things to move off the sofa?)