The Central Bureau for Statistics of the Netherlands reported that in the year 2014 3.5% of the (online) Dutch population, which is an estimated 480,000 people, have been scammed while buying or selling goods or services online. Under Dutch law, this is considered a breach of the civil standard of pacta sunt servanda (i.e.: agreements need to be kept). When the complainant seeks a legal remedy, he will initially have to rely on civil law. Accordingly, the Dutch Supreme Court decided that the mere intentional breach of a purchase agreement is not punishable under article 326 (deceit) and 321 (embezzlement) of the Dutch Criminal Code. These judgements raised the (parliamentary) question if an intentional breach of contract as such should invoke criminal liability. Criminal law is considered to be an ultimum remedium. The determination of whether and under which conditions certain conduct should be criminalised, is a first essential step in the criminalisation process. In some cases enforcement through other areas of the law, such as administrative or civil law, could be considered a better solution for the problem at hand. The question of whether certain conduct should be criminalised requires a careful weighing of arguments for and against criminalisation – all the more where it concerns conduct that is already currently enforced through civil law. How can it be justified to use the far-reaching measures of the criminal law for ensuring compliance with the civil standard of pacta sunt servanda, i.e. to protect private interests between vendor and buyer? This paper analyses the underlying criminalisation principles in the Dutch criminalisation debate on breaches of sale contracts. This analysis aims to provide insight into the legitimacy of criminalising such a breach at the Dutch level, and – in a broader sense – into the legitimacy of criminalising the violation of civil law standards.