LITTLE ROCK — Entergy must rehire a worker it fired over concerns that he would not be able to help defend Arkansas Nuclear One in Russellville from an armed chemical attack, a federal appeals court said Tuesday. The 8th Circuit Court of Appeals in St. Louis upheld a federal judge’s decision that affirmed an arbitration award in the case of Michael Phillips, who was fired by Entergy from his job as a security officer at the nuclear power plant.

In November 2012, after Phillips had been on the job a year, he was ordered to receive a fit test for a full-face gas mask that he would have to wear in the event of an armed chemical attack on the plant. Phillips was then told that he could not be tested because he had a goatee. Phillips has been diagnosed with chronic folliculitis, which causes his hair follicles to become infected or inflamed if he shaves too often.

Phillips filed a grievance over his firing. In March 2015, an arbitrator found that Entergy lacked just cause to fire Phillips because it never fit-tested him to see if he could wear a gas mask properly with facial hair and because it could have transferred him to a position at the plant that did not require being able to wear a gas mask.

In March 2015, the arbitrator ordered Entergy to rehire Phillips with back pay. Entergy filed a lawsuit challenging the arbitration award, and a federal judge in Little Rock granted a motion by Phillips’ union, United Government Security Officers of America, to dismiss the suit. Entergy appealed, arguing that the arbitration award would force it to violate federal regulations, ignore testing and training standards that Phillips’ union agreed to, and create a job for Phillips that does not currently exist.

In its opinion Tuesday upholding dismissal of Entergy’s suit, a three-judge panel of the 8th Circuit said security positions that do not require being able to don a gas mask currently exist at the plant. Entergy has not argued that those positions violate federal regulations or testing and training requirements, the court said. The problems that Entergy cited with rehiring Phillips “are not matters of federal law, but of Entergy practice,” the court said in an opinion written by Chief Judge Lavenski Smith.