EU law largely does not regulate national security matters of the states. Though that justification is limited per international law (such as ECHR, which is the basis of many anti-government surveillance rulings by CJEU). All European Union members are part of ECHR because that is a pre-requisite for EU membership.
But ECHR is not part of EU law, especially it is not binding on the European Commission (in the context of it being a federal or seemingly federal political executive). This creates a catch-22 where member states might be violating ECHR but are mandated by EU law, though this is a very fringe consequence arising out of legal fiction and failed plans to federalize EU. Most recently, this legal fiction has become relevant in Chat Control discourse.
Great Britain and Poland have explicit opt-outs out of some European law.
But ECHR is not part of EU law, especially it is not binding on the European Commission (in the context of it being a federal or seemingly federal political executive). This creates a catch-22 where member states might be violating ECHR but are mandated by EU law, though this is a very fringe consequence arising out of legal fiction and failed plans to federalize EU. Most recently, this legal fiction has become relevant in Chat Control discourse.
Great Britain and Poland have explicit opt-outs out of some European law.