If any flag, post or boundary mark be placed in the course or displaced after the riders have been shown over the ground or have had the course pointed out to them, it shall not be considered binding or of any effect unless such addition or alteration shall have been particularly named previous to starting to all the riders in the race, by one of the stewards, the clerk of the course or by their representative.
N.Y. Comp. Codes R. & Regs. Tit. 9 § 4066.3