I once attended a HoC home affairs select committee where I saw that some Tory members were quite shocked that the EU would require guarantees on the rule of law to both accept the European arrest warrant and police co-operation through Europol. By guarantees, they require adoption of the Charter of Fundamental Rights and enforcement/appeal to the EU Court.
Democratic control of state surveillance is a global problem and one about which most of Europe due it its history is much more attuned. The UK’s current legal framework is the Investigatory Powers Act 2016, proposed by Teresa May, and “opposed” by Andy Burnham and Sir Kier Starmer.
The whole of Labour’s ploy is to create something beyond the EU, to offer to share access to weapons & intelligence in exchange for single market opt-outs, a single market for munitions, but not for labour or people.
They probably want to keep the justice pillar opt-outs too, although given the changing politics of the EU and the Labour government, there is little point. The opt-outs were negotiated to protect the British state against the EU court’s potential interference in UK immigration and labour laws. But escaping the CJEU is not enough; it should also be noted that most of the recent ECtHR losses by the British government have been over the administration of justice, not unexpected when one reviews the recent Home Secretary and Justice Secretary incumbents …