No you cannot ask me for my service animals papers and no she does not need to wear a vest either. The manager argued with me about the rights of my service dog. It is illegal to ask me for papers. "When it is not obvious what service an animal provides, only limited inquiries are allowed. Staff may ask two questions: (1) is the dog a service animal required because of a disability, and (2) what work or task has the dog been trained to perform. Staff cannot ask about the person's disability, require medical documentation, require a special identification card or training documentation for the dog, or ask that the dog demonstrate its ability to perform the work or task.
" taken from http://www.ada.gov/service_animals_2010.htm