Rees, from the London Society, booked all 15 Harrogate players during Saturday's Courage League Third Division game at West Yorkshire rivals, Otley.
The Harrogate captain, Ian Hassal, said: "It's not something we're particularly proud of - we feel incredibly hard done by. This could cost us promotion. We could lose some key players if the decision stands as several of our players were already on a yellow-card prior to the match. Another one means an automatic ban."
The coach, Peter Clegg, said the club would be appealing to the regional branch of the RFU.Reuse content