Do dogs have to wear a collar showing owners name and address in public places?

It is the law in most States in the US and highly recommended, as it means if your dog gets lost, he/she is more likely to be returned to you. It also the law in some countries that rabies tags have to be attached to a dog collar. Some dog harnesses have front rings for ID tags, as an alternative to a dog collar. Laws do not insist on a dog collar specifically, so a dog harness would be fine.