Protocol 36 of the Lisbon Treaty provided that the UK could choose not to accept the jurisdiction of the Court of Justice of the European Union, and the enforcement powers of the Commission, in relation to these pre-Lisbon police and judicial cooperation measures. Consequently, former instruments adopted under the ‘third pillar’ that have not been amended, repealed or replaced since the entry into force of the Lisbon Treaty, cease to apply to the UK. The UK aimed to re-join 35 measures that have been considered indispensable for UK security, however, opting back it would be irrelevant in case of Brexit. Rather than replicating the UK government reports focusing on UK police and justice official’s input to analyse opt-out implications, this paper focuses on the actual value of such practitioner consultation in the process of rulemaking or abolition. Analysing the UK government reports, it seems that EU instruments are crucial to UK policing. However, previous research on EU instruments concluded that practitioners were opposed and criticised their implementation into policing practice. It could follow that practitioner consultations to address the effectiveness of a measure are of limited usefulness. The broader question posing itself is, however, what law makers should then consider instead when establishing regulation.