One immediately striking feature of the law in the area of sexual offences is that the idea of a distinct body of sexual offences is relatively novel. By this I mean that the idea of sexual offences as a distinct sub-field of the criminal law, organised around a the protection of a distinct interest or wrong or according to a central governing principle, is a fairly recent development in the criminal law. The term sexual offences was not used in any legislation in the UK until 1956, and not in the US until the Model Penal Code in 1962, and, while occasionally used as a descriptive term in treatises before this date, it was little more than a usage of convenience, a way of describing a sub-category of offences against the person. It was not until the 1970s that the idea of sexual offences began to change from being a descriptive grouping to something that reflected an underlying organizing principle - that of the protection of sexual autonomy.
This led to some notable instances of decriminalization of consensual sexual conduct seen as inconsistent with the idea of sexual autonomy - notably the decriminalisation of homosexual conduct - and this is usually seen as the major development in this area. However, arguably the larger impact has been in terms of increased criminalization, as the recognition of this distinct interest in sexual autonomy has led to the identification of a growing range of ways that this can be infringed or interfered with. Recent legislation on sexual offences in the UK has thus criminalized voyeurism, sexual grooming of children, 'sexting', sexual interference with a corpse, possession of extreme pornography, sex with trafficked women and many more. The point here is less that of whether or not these should be crimes (many of them already were, but were not seen as sexual crimes), than to ask the question of how it is that they come to be classified as sexual offences - and more broadly to ask whether the recognition of the category might not have an expansionary logic.
This suggests that before we can take the idea of a category of sexual offences for granted and think about how it is best organised or regulated, it is necessary first to ask about how it is that certain behaviors been grouped together under the rubric of sexual offences, about the kinds of connection or thematic unity that makes this grouping possible, and about the consequences for criminalization of thinking in categories of this kind.