I know that posts about buying/selling miles get taken down but I have a legitimate good-intentioned question that I have been unable to track down:

Does Amex prevent the selling of membership rewards points? I know that airlines explicitly restrict this (and AA will even sue you in court) but I've looked over the Amex terms and can't seem to locate any similar restrictions. Is this a grey area or am I just completely missing where this language is included? Thanks!