Three-year-old Sam Spiteri was born with a form of cerebral palsy that makes it hard for him to do ordinary tasks such as walk, hold toys, eat or speak.
The youngster has been riding his miniature pony, Emily, since he was an infant.
"Taking her away would be devastating to Sam. It is his best friend," said his mother Antonia Spiteri.
He's so attached to the animal that his rides usually end in tears because he doesn't want to leave Emily.
But a neighbour's complaint about the animal's smell is now being handled by the Town of Caledon, whose bylaw enforcement manager has ruled the Spiteris' half-hectare property is zoned rural-residential, meaning they cannot keep livestock.
The Spiteri family, however, argues Emily shouldn't be classified as livestock because she was bought as a form of therapy.
"We only want the exception for Emily herself to remain on the property for therapeutic purposes," said Antonia Spiteri.
Sam's grandfather bought him the pony because the youngster experiences seizures, making it almost impossible to take him on long car trips to a riding facility elsewhere.
According to the Ontario Cerebral Palsy Foundation, equestrian therapy "improves balance, co-ordination, strength and muscle tone, while gently mobilizing the joints."
Antonia Spiteri says Sam's pediatrician suggested the riding therapy, and they have seen an improvement in his posture.
"Bouncing from riding her triggers the muscles to stiffen and contract, so that when he rides her, he gets better posture and makes it easier for those muscles to learn those types of things. And then he is better with possibly walking in the future," she said.
"When his posture is better, it's easier for him to perform simple tasks such as feeding himself. It also helps with speech."
The debate over whether Emily can stay on the property will now go before a committee of adjustment.