The employees, one of whom has worked at a rec center for 34 years, disclosed to the city that they had other public-sector jobs, Spear said. The city even recruited some of the teachers because their expertise in education was helpful at the rec centers, he said.
"How can you, after hiring and approving their retention, come out and say, OK, well, now we have to fire you?" asked Spear, attorney for District Council 33 of the American Federation of State, County and Municipal Employees. "If you're lax in enforcement, you're now establishing what the rules should be."
The matter likely will go before an arbitration panel.
City Inspector General Amy Kurland, whose "double-dipping" investigation led to the firings, said that past administrations' failure to enforce the rule does not make violations appropriate.
"Our job is to discover situations where the rules and regulations are not being followed, and these are one," she said.
Kurland added that the workers are not accused of wrongdoing and will be able to keep their full-time jobs.
"It's not like they're going to be out on the street," she said. "I don't think it's a huge inconvenience for anybody. . . . It also opens up these jobs to people who need jobs."
The issue made headlines in 1994, when a city controller's audit found that legendary swimming coach James Ellis, famous for turning poor North Philly kids into Olympians, was violating the rule as both a math teacher at Bodine High School and a coach at a city pool in Nicetown.
Coincidentally, Deputy Mayor for Environmental and Community Resources Michael DiBerardinis, who oversees Parks & Rec, was recreation commissioner at the time as well. He helped then-Mayor Ed Rendell's administration find a legal work-around to keep Ellis on board after public scrutiny of the near-firing.
Then, as now, DiBerardinis initially said the city had no choice but to enforce the rule once violations became apparent. He said the issue came up this time when human-resources workers at the department notified Kurland's office about employees who self-reported their dual employment.
"[A] bunch of them . . . basically said they are working at another job that's within the public sector. . . . The Law Department came in with an opinion that this was . . . in violation of the Charter," he said. "What we're trying to do is become consistent."
Kurland said her office is reviewing payroll data for all executive-branch employees to find out if more are violating the Charter. She said she suspects there are more at Parks & Rec and others at the Department of Human Services.
On Twitter: @SeanWalshDN