Kewl... didn't mean to upset you... I really think that any dog specially trained to assist someone who is disabled, be that physically, emotionally, psychologically or all, should receive special privileges.
Of course, nowdays there are tons of people who are ruining it for us, aren't there? Claiming their cutesy pocketbook dog is specially trained just so they can carry him about.
There's no national rules... but there are State expectations. Since there's no basic certifications required, it's good that the ADA has a few limiting declarations, imo.
My service dogs have always done double duty for me...and of course weren't taught how to respond to the emotional or pain, stress driven aspects of my disabilities.
Most trainers though will say that unless your service dog is over 10 yo, not to have another dog in the home. Wonder if this is an old wive's tale upon which their opinion is based?