One paced calmly beside Linda Wiedewitsch, a retired police officer who now trains assistance dogs for veterans with post-traumatic stress disorder.

“Can my dog meet your dog?” the other shopper asked. “No, sir,” she said. “This is a service dog.”

“Well, this is a service dog, too,” the other shopper said, as his puppy squirmed and yapped through the muzzle it was wearing.

“No, sir,” she said. “It’s not.”

More service dogs are being trained to help people with a wider range of disabilities than ever before. They can tell with one sniff whether someone with diabetes is having trouble with their blood sugar, or if a child with a life-threatening allergy is about to bite into something dangerous. They can pull wheelchairs, wake ­veterans from their night terrors, or remind their elderly owners to take their medication.

Many of these conditions are invisible, unlike the dogs in their bright service vests. That can create confusion for businesses unsure of the line between their “No Dogs Allowed” policies and the laws that protect the rights of ­people with service dogs.

Adding to the confusion, anyone can go online and buy a service dog vest for their pet. That, advocates say, is making it even harder for people with trained service dogs to convince sometimes-skeptical businesses that their dogs are there to do a real job.

The Minnesota Department of Human Rights fields complaints about restaurants, landlords, businesses and taxi drivers who don’t realize state and federal laws allow service dogs to go anywhere a ­customer can.

Many issues are settled with a quick phone call to the businesses explaining the law, but there have been seven full investigations of service-animal-related violations of the Americans with Disabilities Act over the past four years.

In Brainerd this summer, a restaurant refused to seat Paul Connolly, a veteran paired with one of Wiedewitsch’s trained Patriot Assistance Dogs, inside with his dog, Cooper.

“They said the dog could eat outside [on the patio] with the other dogs,” said his wife, Nancy Connolly, who was with him during the late June confrontation. “I told them this wasn’t any dog — this is a service dog.”

The Minnesota Legislature beefed up protection and access rights for people with disabilities and their service dogs last year, after Judy Mielke, who is blind and who uses a wheelchair, was not allowed to bring her service dog into a Rochester restaurant, where she was trying to enjoy a Mother’s Day brunch with her mother.

“These dogs offer an incredible service to people with disabilities and our veterans,” Gov. Mark Dayton said at the time. “No Minnesotan should be denied service in a restaurant or business, ­simply because they need a service dog to go about their daily lives.”

Setting restaurant straight

Some businesses are under the mistaken belief that they don’t have to allow service dogs inside if there are other concerns — say, a crowded room or another customer who’s allergic or afraid of dogs, said Minnesota Commissioner of Human Rights Kevin Lindsey. But none of those concerns trump someone’s right to move freely about the community with the assistance they need, he said.

“Typically we resolve [disputes] pretty quickly, because there’s not generally a factual dispute,” Lindsey said. “The business owner takes the position that they have the discretion to reject the individual because of health concerns or customer preference.” The state then explains to the business that they’re wrong about that.

There are no training standards or national certification requirements for service ­animals.

The only questions business are legally allowed to ask are: “Is that a service animal?” and “What service is it trained to perform?”

Joe Buzay gets looks sometimes when he walks into shops with Frankie, an 80-pound boxer-husky mix by his side. He and Frankie, a blue-eyed charmer of a mutt, were one of the first teams paired through the Patriot Assistance Dogs program.

“I’ve had a couple [of businesses] say something to me,” said Buzay who, like all the veterans in the PAD program, received his dog free of charge. “I’ve got a hot temper and a big mouth. If somebody says something to me, I’ll light ’em up.”

Before Frankie, Buzay said, he was a virtual hermit, self-medicating with pills and barely leaving the house.

“I was just tired of life. I couldn’t deal,” Buzay said. “He saves me from myself, plain and simple.”

Certification online

At the Minneapolis-St. Paul International Airport last weekend, a line of trainee service dogs wagged their way through the metal detectors. The dogs are in training with Can Do Canines, which has paired more than 750 human and canine teams over the past 25 years. Training events, like last Saturday’s airport outing, ensure that the dogs know how to behave when it comes time to board a plane.

Service dogs fly free, which could present a temptation for someone with an Internet connection and without scruples. A quick online search turns up plenty of companies offering to certify your dog, sight unseen, as a service or therapy animal.

“It’s no secret that many businesses simply aren’t pet-friendly, even though most of the population is,” notes one site, the National Service Animal Registry, which offers a “Complete Service Animal Certification Kit” for $64.95. “A large number of our clients register their dogs as Certified Service Animals not just to accompany them into stores, restaurants, motels, or on airline flights [for no extra cost], but to successfully qualify for housing where pets aren’t allowed.”

It’s not illegal. Company spokeswoman Courtney Livingood noted that the Americans with Disabilities Act allows people to train their own service animals, and having a vest and documentation cuts down on questions.

Demand for the service has skyrocketed, she said. In 2010, National Service Animal Registry sold 1,000 kits for “emotional support animals.” In 2013, it sold more than 13,000.

“We do our best” to ensure that the people who order the kits have both disabilities and properly trained dogs, she said. “We try to educate the public … We’ve had people tell us, ‘I’m not disabled.’ ” In that case, she said, “We’ll flag them.”

A number of states have made it a misdemeanor to fraudulently represent an untrained pet as a service animal. Minnesota has no such law and focuses most of its regulatory energies on protecting the rights of people with legitimate service dogs.

“You would hope that people wouldn’t use this in a manipulative fashion, but unfortunately there’s always going to be one or two proverbial bad apples on the tree that are going to take advantage,” said Human Rights Commissioner Lindsey. “But I don’t think that takes away from the overall benefit that comes from providing greater opportunities for individuals with disabilities.”