Regulation has increased in recent years in terms of both quantity and complexity. As a result, the familiarity of the law by citizens is under pressure. This research examines in what circumstances and for what reasons citizens can invoke ignorance of the law (‘legal ignorance’) against their contracting parties and what responsibility the government has in that context. Who ultimately bears the risk of unknowable rules of conduct turning out to be different than expected, and why? Research into Belgian case law and legal doctrine will be complemented by a comparison with Dutch law, German law and the law of England and Wales. This foundational research into how the systems under study align the interests of contracting parties with those of each other and the taxpayer is necessary to improve our understanding of the possibilities and limits of regulation as an instrument within the framework of a democratic Rechtsstaat.