Chopper the Biker Dog, a 5-year-old Boston terrier, lost his therapy dog certification for wearing his costume while visiting people at San Diego veteran’s hospitals, senior centers and schools, according his owner.

Mark Shaffer, who has worked with therapy dogs for a decade, told ABC News today that Pet Partners, the certifying agency, had full knowledge that Chopper had been wearing his costume – a leather vest, biker goggles and a bandanna – for years.

“I’ve been doing this for 10 years and they’ve acknowledged that I do this,” he said. “As soon as Chopper rides into someone’s room on his motorcycle, the patients start to laugh and smile. Each therapy dog brings something different to the table and Chopper’s whole package provides the therapy.”

Chopper lost his Pet Partners therapy certification for wearing his "biker dog" costume on visits in San Diego.(KGTV) Chopper lost his Pet Partners therapy certification for wearing his "biker dog" costume on visits in San Diego.

Chopper was certified with Pet Partners – formerly The Delta Society – for five years and Shaffer’s previous dog, Bandit, was certified for five years as well.

Shaffer's reaction when he found out Chopper was decertified?

"Disbelief," he told ABC affiliate KGTV in San Diego. "There was anger and there was a lot of hurt.”

Pet Partners has a policy prohibiting costumes, citing safety for both the handlers and their pets and the patients they visit.

“It’s not a problem for dogs to wear costumes around town, but in the context of a therapeutic visit it’s not appropriate,” Glen Miller, the national director of communications, told ABC News today.

Miller noted that Pet Partners has over 11,000 teams of handlers and pets across the country and it’s hard to monitor that everyone follows this rule. Shaffer was mailed a warning about a year ago about Chopper’s costume, Miller said.

Pet Partners suspended Chopper on May 14, Shaffer said, adding that Chopper’s visits were always on his own time and not organized by Pet Partners.

Shaffer said that he plans to get Chopper certified with another organization and continue to keep Chopper’s biker dog image.

"It’s not a costume," Shaffer said. "It’s his persona."