Reg. subletting

our society has recently implemented the rule of charging 10% of service charge as subletting charges, now one of our memeber who also happens to be ex-seceretary of the society and was incharge for last 3 years has a flat on rent from last 7 years and was paying Rs. 120 as subletting charges all these years as decided in our earlier meeting during the year 1997. now he is asking to refend the amount he had paid from year 2003 till date to the society. my question is is he liable for refund as the new 10% charges is implemented from may 2009 onwards.