From the Darts Regulation Authority Rule Book.
5.25 Playing Attire:
5.25.01 Players are not permitted to wear jeans: neither shall they wear trousers or skirts made with denim or corduroy material which have been fashioned in a “jeans style”. No training shoes will be allowed unless the Player provides written medical reasons from a qualified practitioner. This restriction shall also apply to any form of “track suit” attire.
5.25.02 No headgear, other than on religious grounds, or medical grounds with written medical reasons from a qualified practitioner, shall be worn without the prior permission of the Promoter following a written application from the Player.
5.25.03 Players are not permitted to wear anything over their approved Playing Attire in any introductions, match play on stage, interviews and presentations, other than at the discretion of the Promoters.
5.25.04 In all Darts Events the Playing Attire of any participating Player shall be subject to the Promoter’s approval. Any unacceptable Playing Attire must be changed before that Player can participate in any introductions, Match play on stage, interviews and presentations.
5.25.
05 Any Player refusing to meet with a Promoter’s requirements in respect of
that Player’s Playing Attire shall be liable to forfeit that respective match and shall be reported to the Council of the DRA for disciplinary proceedings to be considered.