If I remember correctly, you need a doctor's note to register an animal as an emotional support animal. I don't believe they have to have certain behaviors like a service animal does, but they do have to have general manners. Depending on where you feel you might need your dog to accompany you will tell you whether you need a service dog or emotional support animal. Emotional support animals are a bit easier to certify, but do not have the same access rights as service animals. There is definitely some specific law to look into regarding the difference, so that is another thing to consider.