The European Investigation Order (EIO) aims to solve the issue of the cross border collection of evidence. However it also creates more problems, in particular for the need of the executing authority to comply, not only with its own laws and procedures, but also those of the requesting member state, where the evidence needs to continue to be admissible in court. The EIO also covers a broader range of crimes than would traditionally be involved with the EU’s provisions on cross border law enforcement and prosecution. Law enforcement, investigating magistrates, prosecution and forensic scientists will all have to engage with their counterparts, and others from other EU jurisdictions. They will have to negotiate the gaps in the EU legislation. Onuf style constructivism is the key to understanding the processes that these professionals will have to engage in in order to make the EIO work in practice.