Advertising Standards Agency in the past year (a Kane and Lynch ad and Condemned 2 ad were the only offenders). However, according to a report from MCV, the ASA will publish new guidelines for gaming advertisements in September which will suggest publishers consider the "wider context of the impact their ads have," rather than simply fulfill the ASA's base requirements.
Basically, the ASA is suggesting that publishers think about whether their advertisements will "offend and cause distress" throughout their ad consumers. Though the ASA admits that violent game ads have yet to be a problem in the UK, it'll use the new guidelines to "qualify the existing guidance to help publishers avoid problems in the future." That statement just confirms our long-held suspicion that the ASA is full-to-brim with psychics.