mini soccer playing up a year u10 u11?

we have a player a year younger than our age group who has played for us for a year at u10 level we are now u11 going into the newly introduced 9 aside we had confirmation email from the yel league in January saying he could stay with us however now they are saying no I know last season they allowed u10s to play in u11s 9 aside but there saying that was the pilot season for 9 aside now there going to keep it they have set the rules and u10 cannot play in u11 we are devastated as he is part of the team and now has to rush around to find another team which will be hard for his parents as his brother plays for us does anyone know of any examples of this being allowed so we can appeal we know of one in another league but need more to make a strong case