The union that represents the bulk of Metro’s transit officers has filed suit in U.S. District Court in Virginia asking that WMATA reinstate an officer who the union maintains was wrongly terminated.

According to court documents, Sherman Benton, a Metro Transit Police officer, was fired by Metro in April 2011 after an investigation into an incident in Atlantic City while he was off-duty and traveling with a female companion. The pair allegedly were involved in a physical altercation. Police were called, and Benton was taken into police custody. He was charged with causing bodily injury to his girlfriend, court papers said. The charges were ultimately dropped.

The suit says that when Benton returned to work, Metro police conducted its own investigation of the incident.

The transit authority concluded that Benton lied to Metro investigators when recounting what happened and because of that terminated him, according to court documents.

Benton’s case was appealed and went to arbitration. In March of this year, an arbitration board ordered that Benton’s firing be rescinded and that he instead be suspended for a year, court papers said.

In May, Benton was placed on paid administrative leave, according to court filings. The filings did not say whether Benton had returned to his job before he was placed on paid administrative leave. Efforts to reach Benton and the lawyer representing the police union were unsuccessful.

In August, the Maryland commission that certifies law enforcement officers in the state declined to re-certify Benton. As a result, Metro has refused to reinstate Benton because officials say he lacks the credentials needed for employment on the Metro police force. Union officials argue that Metro has allowed transit officers to work even if they lacked proper certification in Maryland.

Metro officials declined to comment on the suit.