I am not a lawyer, but did two or three modules on UK contract law in uni (several years ago). IMHO Emirates had the right to do this as this possibility was announced during the time of booking. The only backdoor I can spot based on the information at hand is that Emirates might not have had sufficient reason to doubt the legitimacy of the booking... messy though and difficult to prove (keep in mind that your friend has to proof this, not EK that they were right).

By all means, I would go for it and try anything possible to get one fare refund, but you friend should not get his hopes up too high. Good luck.