By the time this book is published it will be about three years ago that Avril McDonald suddenly passed away, at the age of 44, on 13 April 2010. She left behind a large group of friends and colleagues and a lot of unfinished projects. There was so much that she had wished to achieve and that she was passionate about: her friendships, her research projects, her students. Avril lived an intense life in which she demanded much of herself and of others, including her students, in order to realise the best achievable results. She could be very critical of herself and could be very straightforward to others, but her enthusiasm and humour made it acceptable to everyone. Avril had worked very hard to reach the position which she had attained in 2010. In May 2009 she was appointed as Rosalind Franklin Fellow in International Law and Contemporary Conflict at the University of Groningen in the Netherlands and in 2010 she would have become adjunct professor and entitled to use the title of professor. In this professorship she would have combined her expertise in international humanitarian law (IHL) with questions related to the use of force in international law, in particular on the role of non-state actors in international conflict. Avril graduated in law in 1987 at Trinity College, Dublin. However, the first years of her career were not dedicated to law but to journalism as she obtained a graduate diploma in journalism in 1988 and worked for various journals and magazines in Ireland, Australia and the USA, mainly in New York. In 1995 she had returned to the study of law and obtained an LLM in Human Rights and Emergency Law from Queens University in Belfast.