What can a business in Hawaii ask about my service dog?

What the law says

28 C.F.R. § 36.302(c)(6): 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." It "shall not require documentation, such as proof that the animal has been certified, trained, or licensed as a service animal."

Source: 28 C.F.R. § 36.302(c) (DOJ ADA service-animal regulation) ↗

In plain language

Under the federal ADA — which applies in Hawaii — public accommodations are limited to two questions: (1) is the dog required because of a disability, and (2) what work or task has the dog been trained to perform. Staff cannot demand certification papers, ID cards, vests, registry membership, or proof of training. Staff also cannot ask about the nature or extent of the disability. If staff exceed those limits, the next step is generally a complaint to the U.S. Department of Justice or to the Hawaii attorney general's civil-rights division.