WASHINGTON — A Metro mechanic fired after an investigation into the deadly smoke incident near L’Enfant Plaza showed he had falsified records must be allowed back on the job, a federal judge ruled Wednesday.

The ruling — in a lawsuit filed by the union against Metro and first reported by WTOP — upholds an arbitration panel decision that reduced Seyoum Haile’s penalty for the falsified fan test records to a six-month suspension due to lax oversight from supervisors and Metro’s failing safety culture.

Judge James Boasberg’s ruling acknowledged that firing Haile may have been consistent with Metro’s efforts to improve the safety of the rail system, and “may even have been the more just outcome here,” but found that courts have limited ability to overturn arbitration decisions that are within the confines of contracts and other agreements.

“As the Award meets the low bar required for confirmation, the Court has little choice but to grant Local 689’s Motion,” the ruling said.

In addition to Boasberg finding that Metro failed to meet legal burdens for overturning the arbitration award, he suggested that Metro had also failed to challenge the ruling before a deadline that would have been required for action.

“Mr. [General Manager Paul] Wiedefeld is now left with no alternative other than to follow the law and stop trying to scapegoat a single employee for the systemic incompetence of his management team that lead to the incident and the death of a rider and injuries to many,” Amalgamated Transit Union Local 689 said in a statement after the ruling.

Wiedefeld did not join Metro until late 2015, months after passenger Carol Glover died outside L’Enfant Plaza.

“Wiedefeld is 0-2 in taking ATU Local 689 to court when he doesn’t like an arbitration decision,” the union statement said. “If Wiedefeld is truly interested in improving relations with his employees, as he has said, then he will stop his waste and misuse of WMATA funds and follow the law.”