But why? A disabled person needs a special license plate or placard to park in a handicapped parking space. How is that any different than a service dog needing a special license or registration?
I don't think the ADA should provide a way for people to bring untrained and potentially dangerous animals into public places or private businesses (like Disney).
The simple answer is that the Justice Department regulations (28 C.F.R. 36.302(c)(6)) specifically limit when a public accommodation may ask about a service animal:
A public accommodation shall not ask about the nature or extent of a person’s disability, but may make two inquiries to determine whether an animal qualifies as a service animal. A public accommodation may ask if the animal is required because of a disability and what work or task the animal has been trained to perform. A public accommodation shall not require documentation, such as proof that the animal has been certified, trained, or licensed as a service animal. Generally, a public accommodation may not make these inquiries about a service animal when it is readily apparent that an animal is trained to do work or perform tasks for an individual with a disability (e.g., the dog is observed guiding an individual who is blind or has low vision, pulling a person’s wheelchair, or providing assistance with stability or balance to an individual with an observable mobility disability).
The regulations also permit exclusion of a service animal if it is out of control or not housebroken, but the public accommodation must then give the disabled person the "opportunity to obtain goods, services, and accommodations without having the service animal on the premises." The definition of service animal is also not as broad as many people think. Work is the key point:
Service animal means any dog that is individually trained to do work or perform tasks for the benefit of an individual with a disability, including a physical, sensory, psychiatric, intellectual, or other mental disability. Other species of animals, whether wild or domestic, trained or untrained, are not service animals for the purposes of this definition. The work or tasks performed by a service animal must be directly related to the individual’s disability. Examples of work or tasks include, but are not limited to, assisting individuals who are blind or have low vision with navigation and other tasks, alerting individuals who are deaf or hard of hearing to the presence of people or sounds, providing non-violent protection or rescue work, pulling a wheelchair, assisting an individual during a seizure, alerting individuals to the presence of allergens, retrieving items such as medicine or the telephone, providing physical support and assistance with balance and stability to individuals with mobility disabilities, and helping persons with psychiatric and neurological disabilities by preventing or interrupting impulsive or destructive behaviors. The crime deterrent effects of an animal’s presence and the provision of emotional support, well-being, comfort, or companionship do not constitute work or tasks for the purposes of this definition.
This is limited to the ADA. There are other federal statutes which might broaden the definition of a "service animal" but these acts do not apply to WDW or DL. I can't say what Florida or California law might require. I suspect Florida's disability law is the same as the ADA. According to this website (which is a California state government site), California also has a law prohibiting misrepresentations of service animals and California law does not seem to require more than the ADA.
https://www.dor.ca.gov/DisabilityAccessInfo/DAS-Docs/SERVICE-ANIMAL-LAWS.pdf