Twenty-one states have in recent months mounted crackdowns on people who falsely claim their pets as service and support animals so they can bring them into restaurants, theaters and other public places, NBC News reported.

But it's not entirely clear how widespread the problem of fake service dogs is.

That's because there is no uniform nationwide certification or registration process for legitimate service animals — which receive up to several years of specialized training — making it easy for people to scam a non-existent system.

And the easy availability online of "service dog" harnesses and vests is all too tempting for animal-owners who want company running errands and going out.

Emotional support animals, with the exceptions of those helping veterans suffering from post-traumatic stress disorder, aren't protected under the Americans with Disabilities Act.

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