Ill. Admin. Code tit. 11 § 1413.110
All entries and declarations made in overnight races are under the supervision of the stewards, and they may, without notice, refuse the entries of any persons, or the transfer of any entries, and they may also in their discretion, limit entries by providing that no horse shall be entered for two races in any one day unless one is a sweepstakes. However, the owner, or trainer or authorized agent who enters the same horse in more than one race on the same day, must declare said horse out of all races, except one, by scratch time of the day said horse is so entered. In any overnight race where a person has entered more than one horse and there are horses on the also eligible list, the owner, trainer, or authorized agent must declare one horse out of said race by the regular scratch time or both horses must start in said race unless excused by the stewards for just reason.
Ill. Admin. Code tit. 11, § 1413.110