Some context. The dress code and rules for enforcement are created by the players' representatives commission in FIDE, consisting of active and former competitive players [1] [2].
In a presentation shared with the players about the dress code before the event, jeans are listed on a slide titled "What's NOT allowed?" with "Not Approved" stamped in big red letters over a picture of jeans [3]. FIDE CEO says jeans have been banned in this event since 2018, and that players were asked for feedback on the dress code before the event, and none complained [4].
The same dress code presentation shared with players also has instructions for the Chief Arbiter:
The dress code is strictly enforced to maintain a consistent level of professionalism and respect for the event. The Chief Arbiter, in consultation with the FIDE Athletes Commission, will ensure that the dress code is upheld.
First Infringement
A financial penalty of 200 € for open events and 100 € for women's events. The player is allowed to play the current round.
Further Infringements
Exclusion from the pairings for the next round. Each round counts as one infringement.
Other top players were also asked to change their attire when found in violation. The hotel is a few minutes away [5]. Magnus Carlsen was notified of his violation after his second game on day 2 (round 7) and asked to change into approved attire before the third round of the day (round 8), played half an hour later [6]. Since he declined, he was excluded from playing in the last round of the day (round 9). This counts as a forfeit, and combined with Magnus' score until that point would make a podium finish unlikely, although he would still have been allowed to play in subsequent rounds [7].
In an interview, Magnus stated he was not having the best tournament, explained he had already lost his patience with FIDE due to an ongoing feud over the freestyle chess championship, and stated he declined to change into approved attire as a matter of principle and would withdraw from the rapid tournament and also the upcoming fide blitz tournament, apologizing to fans at home [8].
In a presentation shared with the players about the dress code before the event, jeans are listed on a slide titled "What's NOT allowed?" with "Not Approved" stamped in big red letters over a picture of jeans [3]. FIDE CEO says jeans have been banned in this event since 2018, and that players were asked for feedback on the dress code before the event, and none complained [4].
The same dress code presentation shared with players also has instructions for the Chief Arbiter:
Other top players were also asked to change their attire when found in violation. The hotel is a few minutes away [5]. Magnus Carlsen was notified of his violation after his second game on day 2 (round 7) and asked to change into approved attire before the third round of the day (round 8), played half an hour later [6]. Since he declined, he was excluded from playing in the last round of the day (round 9). This counts as a forfeit, and combined with Magnus' score until that point would make a podium finish unlikely, although he would still have been allowed to play in subsequent rounds [7].In an interview, Magnus stated he was not having the best tournament, explained he had already lost his patience with FIDE due to an ongoing feud over the freestyle chess championship, and stated he declined to change into approved attire as a matter of principle and would withdraw from the rapid tournament and also the upcoming fide blitz tournament, apologizing to fans at home [8].
[1] https://doc.fide.com/docs/90%20Congress%20Agenda%20and%20Ann...
[2] https://www.fide.com/directory/commissions (GM Ahmed Adly, GM Eugenio Torre, IM Dinara Saduakassova, WIM Jesse Nikki February, GM Irina Krush, GM Wei Yi, IM Alina Kashlinskaya, IM Oluwafemi Daniel Balogun, IM Noaman Omar, GM Ioan-Cristian Chirila, IM Irine Kharisma Sukandar, GM Ivan Cheparinov, GM Evgeny Tomashevsky, WGM Aleksandra Dimitrijevic)
[3] https://doc.fide.com/docs/2024_WRBC/wrbc2024_dress_code.pdf
[4] https://www.youtube.com/watch?v=NWi5CIKhuSs [ Magnus Carlsen Jeans Scandal | Full Story ] from 15m00s
[5] https://www.fide.com/news/3363
[6] https://www.youtube.com/watch?v=PrK88j-fyaw [ FIDE World Rapid Championship 2024 | Rds 6-9 ], Magnus' round 7 game finishes around 2h24m30s, round 8 2h59m50s
[7] https://www.facebook.com/chess/videos/-magnus-carlsen-is-unp...
[8] https://www.youtube.com/watch?v=NWi5CIKhuSs [ Magnus Carlsen Jeans Scandal | Full Story ] from 3m28s