Abstract In the absence of the country of origin principle and thus quasi-automatic mutual recognition, the creation of codes of conduct (CoC) at a European level as an alternative, soft-law method of rule-making acquires new dynamics. CoC are an example of self-regulation by associations of undertakings. CoC, while voluntary, soft-law instruments, are considered as partaking in the effort to increase the ‘awareness of Europeanness’; pursue legitimate objectives that are accepted as valid at EU level; and ultimately guarantee a high level of quality commensurate with the ever-increasing expectations of the EU citizens with a view to enhancing trust among MS as to the equivalence of services and service suppliers originating in other MS. Such rules of conduct, which are typically adopted by non-state bodies (professional associations) when they exercise their legal autonomy, can hinder the intra-EU free movement of professionals. Hence, liberalization of factor mobility enshrined in primary and secondary EU law can be jeopardized by the adoption and application of such codes, which are also foreseen in the Services Directive. This paper aims to explore the impact of CoC on further liberalizing professional services within the EU. It critically reviews the soft-law approach adopted by the EU in this area. Finally, the paper analyses the possible content of such CoC and its compatibility with EU law, notably the rules on free movement and competition.