This study examines the first judgment of the Court of Justice concerning the confidentiality of communications between lawyer and client (i.e. "legal privilege", "LP"), delivered in AM & S Europe v Commission, Case 155/79, on 18 May 1982, which is among the most frequently cited in Luxembourg case-law. The findings are related to subsequent Luxembourg case-law and to Polish case-law, as well as to the protection laid down in Article 4 of Directive 2013/48/EU and in domestic provisions establishing defence counsel's professional secrecy. This analysis yields the following gradation: – as a rule, full protection of the confidentiality of the relationship between an independent lawyer and the client in the case-law of the Court of Justice, influenced by the case-law of the European Court of Human Rights, and in Polish constitutional jurisprudence and the case-law of the Polish Supreme Court, subject to two Code provisions that depart even from the State's duty of abstention, a departure endorsed by the Constitutional Tribunal within a defined scope; – narrower protection in Polish law on a literal interpretation; – a marginalisation by the Court of Justice of Article 4 of Directive 2013/48/EU, which, on a literal construction, establishes only a duty of abstention; – finally, the case-law of the Polish ordinary courts is the least predictable.