Chiles initially scored 13.666 in Monday’s final, putting her in fifth place in the competition and leading Romanian gymnast Barbosu, who scored 13.7, to believe she had won the bronze medal.
However, after the inquiry by Chiles’ coach Cecile Landi with regard to her difficulty rating, officials upgraded Chiles’ score to 13.766, placing her third.
The adjustment left Barbosu, who had begun celebrating her medal, upset and led to a protest from the Romanian team.
Romania’s prime minister Marcel Ciolacu called it a “scandalous situation” and threatened to boycott the closing ceremony.
The Romanian Olympic Committee successfully appealed to Cas on the grounds the inquiry was “untimely” as it had been submitted four seconds after the one minute time limit.
Cas reinstated Chiles’ score of 13.666 on Saturday, which was later confirmed by Fig.
The International Olympic Committee said it will reallocate the bronze medal to Barbosu and is in touch with the US team regarding the return of the medal and the Romanian Olympic Committee to discuss the reallocation ceremony.
USA Gymnastics and the US Olympic and Paralympic Committee said: “The inquiry into the difficulty value of Jordan Chiles’ floor exercise routine was filed in good faith and, we believed, in accordance with Fig rules to ensure accurate scoring.”
Speaking about the online abuse of Chiles, they added: “No athlete should be subject to such treatment. We condemn the attacks and those who engage, support or instigate them. We commend Jordan for conducting herself with integrity both on and off the competition floor, and we continue to stand by and support her.”
Chiles’ team-mate Simone Biles won silver in the event, with Brazil’s Rebeca Andrade taking gold.
On the podium, Biles and Chiles bowed down to Andrade in an iconic moment of the Games.
Biles posted her support for Chiles, writing: “Sending you so much love Jordan, Keep your chin up Olympic champ, we love you.”
Fellow US gold medal-winning gymnast Sunisa Lee posted: “All this talk about the athlete, what about the judges? Completely unacceptable, this is awful and I’m gutted for Jordan.”