Due to new regulations in New York City, dog owners living in public housing must either move or give up their dogs.

Tyson was a tough-looking, head-turning dog — a 60-pound, year-old Staffordshire bull terrier with a silver-gray coat and blue eyes. But the only thing tough about him was his name, his owner said.

Tyson followed commands, never bit anyone and liked to put his paws on people’s heads to play with their hair. “He was a big baby,” said his owner, Marc Hernandez, 20, who had had Tyson since he was a puppy of 7 weeks.

Yet one day in May, Mr. Hernandez, a student at John Jay College of Criminal Justice, took Tyson to an East Harlem animal shelter, where he reluctantly and tearfully surrendered him. The problem was not Tyson’s behavior, but his home: Mr. Hernandez lives in one of New York City’s public housing projects, where a ban on pit bulls and other large dogs went into effect May 1.

The ban, one of the strictest for any public housing authority in the country, prohibits residents from keeping pure-bred or mixed-breed pit bulls, Rottweilers and Doberman pinschers, as well as any dog, with the exception of service dogs, expected to weigh more than 25 pounds when grown.

Read more of Large Dogs in Public Housing Are Now Endangered Species.