(Update - September 2016)
The UK operates one of the most rigorous and transparent export control regimes. All UK arms exports are scrutinised in detail through established processes and against the EU and national consolidated criteria. Neither the Ministry of Defence nor the Foreign and Commonwealth Office reaches a conclusion as to whether or not an international humanitarian law violation has taken place, in relation to each and every incident of potential concern that comes to its attention. This would simply not be possible in conflicts to which the UK is not a party, as is the case in Yemen.
However, the Ministry of Defence monitors incidents of alleged international humanitarian law violations using available information. This is used to form an overall view on the approach and attitude of Saudi Arabia to international humanitarian law. This, in turn, informs the risk assessment made under the consolidated criteria and whether there is a clear risk that it might be used in the commission of a serious violation of international humanitarian law.
The Government has been clear that given the guidance under the consolidated arms criteria and the EU criteria, the level has not been reached where those criteria have been breached.