The starting point for the thesis is the problem of negative externalities public purchasing gives rise to. We argue that public procurement regulation, having as an objective the structuring of public markets for public contracts, produces the said market failure, which may adversely affect the competitive dynamics in other markets. This may cause a significant loss of social welfare. The reason why public procurement produces such negative externalities is, so we argue, due to the fact that public procurement regulation is foremost concerned with the internal dimension of public purchasing, i.e. the relationship between the public purchaser and actual and potential tenderers. However, public procurement regulation largely omits the external dimension, i.e. the effects public purchasing produces vis-à-vis markets outside the specific market for the public contract at hand. In our quest for a way to address this problem of negative externalities we argue that these externalities converge to a large extent with an ‘advantage’, being one of the conditions for the EU state aid prohibition (laid down in article107 (1) TFEU) to apply. Hence, we deem EU state aid law to be a valuable source of inspiration to ‘enrich’ public procurement regulation. Such ‘enriched’ public procurement regulation would be able to avoid the occurrence of the negative externalities we identified, or at least to minimise the risk of their occurrence. Examining a number of areas within EU state aid law allowed us to identify a number of principles that ensure absence of an ‘advantage’. These principles constitute the basis for our ‘standard for enrichment’, i.e. a framework for regulatory reform as to public procurement regulation. We also apply this standard to a number of aspects of public procurement regulation. More specifically, we clarify how ‘enriched’ public procurement regulation would materialise as to the following aspects of public purchasing: (i) the disclosure obligation as to award criteria and their belongings, (ii) the pursuit of policy objectives through public purchasing and (iii) modifications to public contracts in the performance phase.