N.Y. Comp. Codes R. & Regs. tit. 9 § 4026.7
After a horse is drawn into a race, there shall be no transfer nor assignment of any ownership interest in such horse until after such race or until such horse is scratched from such race, if sooner. No member of a partnership that owns a horse, leases the racing qualities of a horse, or is designated a managing owner for a horse shall assign his or her share or any part of or interest in it without the written consent of the other partners being filed with The Jockey Club. No assignment of an interest in a partnership which, by ownership or lease, controls the racing qualities of a horse, shall be accepted if the effect of the assignment would be to create a partnership that would not qualify for filing under the terms of section 4026.2 of this Part.
N.Y. Comp. Codes R. & Regs. Tit. 9 § 4026.7