I have taken a number of airplane trips over the past month or so, and I noticed, on each of the flights I took, that there were dogs on board — not in carriers, but sitting on the laps, or in the arms, of their owners. It struck me as odd, and now, thanks to an interesting and informative article by Karen Elliott and Rebecca Lightle in The Washington Post a few weeks ago, I have an idea about what’s going on.

They’re all, apparently, “service dogs” — though from the look of it, they didn’t appear to be performing (or capable of performing) any particular service, nor did their owners appear to be disabled in any way. As Elliott and Lightle explain, the Americans With Disabilities Act requires places of public accommodation such as restaurants and transportation carriers to allow service animals — which can be dogs or, oddly enough, “miniature horses” — that assist people with disabilities.

That seems fair enough (though the “miniature horses” part seems a little peculiar). The problem, though, is in determining whether any particular animal qualifies as a service animal — and in doing so without running afoul of the ADA’s restrictions on the questions concerning disabilities that the ADA also imposes.

To meet the ADA’s definition, a dog must be individually trained to perform specific tasks that directly relate to a person’s disability. For instance, a service dog may be trained to assist with navigation or alert its handler to safety concerns. However, if a dog provides aid only by its natural behavior, then it lacks the individualized training necessary for ADA accommodation. This standard means that the ADA does not apply to many dogs that function as therapy, emotional-support and companion animals.

So how should a business assess whether a customer’s dog is a service animal? Federal regulations instruct that if it is readily apparent that a dog is aiding a person with a disability — for example, by leading a person who is blind — then staff members should simply allow the dog in as a service animal. But if the dog’s function is not apparent, then the ADA permits only two types of inquiries. First: “Is this dog required because of a disability?” And second: “What specific assistive task or tasks has the dog been trained to perform?”

Not surprisingly, many people are gaming the regulations, claiming “service animal” status for Fido just as a way of getting around restrictions on dogs in restaurants, apartment buildings, etc.

And the situation for airplanes is even worse. The federal Air Carrier Access Act (ACAA) provides even broader protections for service animals.

Unlike places of public accommodation governed solely by the ADA, commercial airlines must accept ID cards, other documentation, apparel or “credible verbal assurances” as evidence that a service animal is legitimate (although an airline may prohibit “unusual” service animals such as reptiles, rodents or spiders). Further, if a passenger with a disability produces appropriate documentation from a licensed mental health professional, the ACAA requires airlines to accommodate emotional-support animals that would not be protected by the ADA.

Service animals accompanying commercial air travelers must be permitted in any seat space where their passenger-handlers are permitted to sit. But federal regulations also instruct airline staff to assess whether a service animal presents a direct threat to the health and safety of others or a significant threat of disruption to the airline service in the cabin. If a dispute arises with a passenger as to whether the animal should be permitted, staff are to refer the matter to the airline’s mandatory complaint resolution official (CRO). Commercial airlines must provide a written explanation to any passenger whose service animal has not been accommodated under these rules.

So just a “credible verbal assurance” books Fido a trip to San Francisco for the weekend. But he better not be sitting next to me. File under “regulatory overreach.”