A discrepancy between New Haven law and police-union contracts nullified the city’s April 2007 termination of a corrupt police officer, and prevented the Board of Police Commissioners from firing another cop arrested for corruption on Thursday.

The ruling underscores the hard-line approach the city, led by the mayor, has tried to take in punishing its officers in light of the corruption scandal that rocked the department last March.

An arbitrator ruled on Thursday that former New Haven Police Department Lt. William “Billy” White — who was arrested in March on corruption charges — could not have been fired by the city because he filed for retirement after he was arrested but before his termination hearing. Under New Haven General Order, the termination would have held. But under NHPD officers’ contract with the police union, retirement is official from the moment the officer files for it.

White is the first cop arrested on corruption charges in recent history to be terminated before he could retire. Since then, the Board of Police Commissioners has pursued the termination of other charged officers: Det. Justen Kasperzyk, Det. Jose Silva and Det. Clarence Willoughby.

But the arbitrator ruled that the union contract supersedes the General Order, effectively setting a precedent for the retirement status and pension schemes for arrested cops who file for retirement before they are officially fired.

The ruling also forced city officials to cancel Det. Clarence Willoughby’s termination hearing, which was originally scheduled for Thursday evening. Willoughby, who was arrested and charged earlier this month for pocketing money from a police informant fund and forging public and police documents, filed for retirement 11 days ago.

Mayor John DeStefano Jr. said on Thursday that the city would pursue changes in the police union contract given to NHPD officers, according to a city press release. DeStefano said he wants to adopt a “Bad Boy Clause,” which will deny cops criminally charged with corruption pension and other compensation and prevent officers from filling for disability compensation to get out of being fired.

“We’re about to enter previously scheduled negotiations with the Police Union for a new contract which presents an opportunity to get the right contract language,” DeStefano said, according to the release.

City Hall spokeswoman Jessica Mayorga said she does not know who the arbitrator is.

White, along with Kasperzyk, was arrested in March following an FBI corruption probe into the NHPD’s narcotics enforcement unit.

White, who served with the NHPD for 39 years, was charged with accepting bribes and pocketing money at crime scenes. Kasperzyk, a 12-year veteran with the department, was charged with stealing government funds.

Both men filed for retirement in March after they were arrested by the FBI. Citing a back injury, Kasperzyk applied for an early retirement on disability grounds.

Mayorga said Thursday evening that the ruling did not affect Kasperzyk’s filing for early retirement.

Days after the BOPC voted to fire White last April, the Policemen’s and Firemen’s Pension Board granted White an annual pension of $91,000. The sum totaled 80 percent of his salary before his retirement plus 40 percent of his average yearly overtime.

But now that his termination has been overturned, White will receive an added $5,000 in pension, Mayorga said, because he will now be entitled to 83 percent of his salary, as retired officers with his level of service usually are.

Kasperzyk’s claim to $41,013 in annual disability pension was approved in September of last year. Silva was not eligible for retirement, but was denied his attempt to resign to avoid termination.

In September, Connecticut Attorney General Richard Blumenthal and Secretary of the State Susan Bysiewicz urged the Board of Aldermen to consider a measure that would reduce or eliminate pension for corrupt police and city employees. Alderman Jorge Perez, who could not be reached for comment Thursday evening, introduced a resolution that would clarify which crimes would affect an employee’s pension.

The arbitrator’s ruling also affects Willoughby, who filed for retirement and, according to White’s precedent, is eligible for pension.

Although NHPD Chief Francisco Ortiz had called for Willoughby’s termination earlier this week, Willoughby pleaded not guilty to internal charges brought up against him by the department on Wednesday.

“While I’ve been adamant about having this hearing to discuss terminating Willoughby, the Arbitrator unfortunately made that decision for us through today’s ruling,” Ortiz said, according to the release. “Read in light of today’s decision, Willoughby’s retirement went into effect 10 days ago and supersedes our general order that positioned us to terminate him.”

Richard Epstein, the chairman of the BOPC, said the ruling made Det. Clarence Willoughby’s termination hearing a “moot point,” the press release states.

According to the press release, Epstein and DeStefano are in agreement that measures should be taken to clarify police contracts and to close existing loopholes.

“We look forward to resolving this issue to ensure a clear understanding of the process and to make sure that rewards are reserved for officers who perform their duties as opposed to those who use a contract to get away with something they don’t deserve,” Epstein said.

Lou Cavaliere Sr., the president of the New Haven Police Union, did not return a request for comment Thursday evening.