Recent social science research suggests that individuals with intellectual disabilities and/or mental illness are particularly vulnerable to sexual exploitation, yet it is rare for successful prosecutions to occur where the complainant has some form of mental impairment. This article critically examines existing sexual assault laws in Australia and New Zealand as they relate to complainants with mental impairment and proposed offences under Division 35 (Sexual Acts Against or With Mentally Impaired Persons) of the Model Criminal Code. Ethical considerations of protection from harm and sexual autonomy are also explored.