Commercial dog walkers do not currently require a licence in most areas, and can operate unchecked with no regulation. I believe a national licence would ensure the safety and well-being of both dogs and the public.
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Walking dogs requires knowledge of dog behaviour, first aid, transport laws, and responsible handling. I believe a licence would establish minimum standards that dog walkers must meet. Currently, walkers may take more dogs than they can handle, which could be unsafe. I believe a licence would regulate numbers. If a licensed walker acts irresponsibly, their licence could be suspended/revoked and this could give incentive to follow conditions.