This paper, written in tribute to a great scholar and friend for more than 50 years, draws on his wide interests in the principles of criminal law, international law and legal process and on the human values underlying them. It also gives attention to some of the lawyer's crafts, especially in the careful drafting of texts and the use of possibly relevant sources and evidences of the law. The paper focuses on individual criminal responsibility, particularly by reference to the principles of non-retroactivity and the certainty of criminal law. A notable American criminal law scholar some years ago brought both principles together in 'the principle of legality': 'a limitation on penalisation... effected by the required prescription and application of specific rules'.