World chess number one Magnus Carlsen has pulled out of a major tournament after being told he could not continue playing while wearing jeans.
The chess great was defending his titles at the FIDE World Rapid and Blitz Chess Championship in New York when officials made the request.
The grandmaster said he offered to change his pants for the next day, but was fined and told he had to change immediately.
The chess federation (FIDE) said the dress code rules were designed to “ensure fairness and professionalism for all participants”.
Carlsen is a high-profile chess figure who has caused some controversy in recent years.
Last year, he settled a long-running lawsuit after he accused a rival of cheating at a tournament.
On Friday, he withdrew from the championships for the short-form versions of the game due to a clothing dispute. Carlsen was the reigning blitz and rapid chess champion.
He added that he would not appeal the decision, saying: “Honestly, at this stage I'm too old to care too much.”
He said he wore jeans to a lunch date and “didn't even think” to change into another pair of pants when he headed into the tournament.
He turned up wearing a shirt, blazer, dark jeans and formal shoes and played a few rounds before being asked to change.
When his offer to switch for the next day was rejected, Carlsen said then “it became a matter of principle for me”.
In a statement, FIDE confirmed the 34-year-old had been fined $200 (£159) and said its rules were applied “impartially”. They cited an instance where another player was fined on the same day before changing his shoes.
Carlsen is a five-time world chess champion and maintains his top ranking in the sport.
The Norwegian has long been considered a fraud in the chess world since becoming a grandmaster – the highest title in chess – at the age of 13.
In a now-settled dispute with opponent Hans Niemann, Carlsen pulled out of the 2022 tournament after Niemann beat him before accusing his American rival of cheating.
Niemann denied the allegations and even said he would “undress completely naked” to prove his innocence.
The couple went on to settle a lawsuit for $100m (£79m) in August last year.