The CEDAW Committee has adopted General Recommendation No. 35 “on gender-based violence against women, updating general recommendation No. 19”. The recommendation complements and updates the guidance to States parties set out in general recommendation No. 19. The CEDAW Committee “regards gender-based violence against women to be rooted in gender-related factors such as the ideology of men’s entitlement and privilege over women, social norms regarding masculinity, the need to assert male control or power, enforce gender roles, or prevent, discourage or punish what is considered to be unacceptable female behaviour”. It points out that the prohibition of gender-based violence against women has evolved into a principle of customary international law, and in this context, emphasises the important role of recommendation No. 19. General Recommendation No. 35 refers to the Council of Europe Istanbul Convention as one of the “landmark political documents and regional treaties” and highlights the importance of the decision by the European Court of Human Rights in Opuz v Turkey (2009) for the determination of customary international law.