Americans with Disabilities Act

THE FEDERAL LAW according to the Americans with Disabilities Act (ADA) 

Service animals are defined as dogs that are individually trained to do work or perform tasks for people with disabilities.  Examples of such work or tasks include guiding people who are blind, alerting people who are deaf, pulling a wheelchair, alerting and protecting a person who is having a seizure, reminding a person with mental illness to take prescribed medications, calming a person with PTSD during an anxiety attack, or performing other duties.  Service animals are working animals, not pets.  The work or task a dog has been trained to provide must be directly related to the person's disability.  Dogs whose sole function is to provide comfort or emotional support do not qualify as service animals under the ADA. 

There are legal penalties associated with misrepresenting a dog as a Service Dog,

There is no government run or official service dog registration body.  The ADA does not require any type of registration nor does it require specific identification.