DVLA sent licence back but was charged with driving without licence as ban was not over

Son lost his licence for 6 mths - received a letter from dvla so he could get his licence back. 3 wks later was stopped by police claiming he was driving without a licence. He had received his new licence from dvla, got his car insurance tax etc and has now been taken to court; got 6 points and a fine, and the car in the police pound. He was informed he should have checked the date before he requested the licence. Where does he stand on this? It must be dvla's fault they are the ones that sent the licence.