Metro train riders are seen being shuttled on a Metrobus after commuters were evacuated from the L’Enfant Metro Station when smoke filled a train. (Ricky Carioti/The Washington Post)

A federal court has ordered Metro to rehire a senior mechanic who was fired in the aftermath of the investigation into the January 2015 L’Enfant Plaza smoke disaster.

But the U.S. District Court judge who wrote the decision, released Wednesday, said he was doing so reluctantly. Judge James E. Boasberg said he could find no legally justifiable reason to vacate the decision awarded by an arbitration board, which concluded that the mechanic should have been suspended for six months without pay, rather than fired.

“The Court has little choice but to grant Local 689’s Motion,” Boasberg wrote. Local 689 is the union that represents the worker.

Metro spokesman Dan Stessel said the agency is “reviewing the decision and considering all options, including appeal.”

The mechanic, Seyoum Haile, was terminated in February 2015, after it was discovered that he had submitted maintenance logs saying that he had successfully performed tunnel fan inspections near the L’Enfant Plaza station, even though he had not properly assessed whether the fans were working.

Burned-out tunnel fans were one of the contributing factors in the Jan. 12, 2015, incident, which killed one woman and sickened scores of other passengers — though investigators determined that the specific fans inspected by Haile did operate properly during the disaster and only began to malfunction after the tunnel had been cleared of passengers.

Even so, Metro fired Haile. But Amalgamated Transit Union Local 689 challenged Haile’s termination, and pushed the decision to an arbitration board. The board ruled that Haile should have been suspended for six months — and should receive back pay for the time he had not been allowed to work after the conclusion of the six-month mark from his termination.

Then, last July, Metro filed its own lawsuit, seeking to vacate the arbitration board’s award.

But Boasberg, in his ruling, said there simply was no legal basis to reject the arbitration board’s decision — even though he clearly sympathized with Metro’s efforts to root out employees guilty of wrongdoing.

“The Court agrees that such a penalty [of terminating Haile] seems wholly consistent with [Metro’s] important efforts to improve the safety of the Metrorail system and may even have been the more just outcome here,” Boasberg wrote.

Still, he said, Metro’s lawyers failed to demonstrate that following the arbitration board’s orders would be a violation of the agency’s own policies or its collective-bargaining agreement with the union. Metro also failed to prove that having Haile back on the job would put the public in immediate danger.

“Placing Haile back to work certainly does not compel him to again shirk his duties, nor does it force the Authority to tacitly condone or assist such behavior,” the judge wrote in his decision.

And, he added, it didn’t help that Metro filed its lawsuit to appeal the arbitration award four months after the decision was made — longer than the 90-day deadline outlined in D.C. law.

“Such a delay in pressing its cause has serious potential repercussions,” Boasberg wrote.