Case C-854/19: Judgment of the Court (Eighth Chamber) of 2 September 2021 (request for a preliminary ruling from the Verwaltungsgericht Köln — Germany) — Vodafone GmbH v Bundesrepublik Deutschland, represented by the Bundesnetzagentur für Elektrizität, Gas, Telekommunikation, Post und Eisenbahnen (Reference for a preliminary ruling — Electronic communications — Regulation (EU) 2015/2120 — Article 3 — Open internet access — Article 3(1) — End users’ rights — Article 3(2) — Prohibition of agreements and commercial practices limiting the exercise of end users’ rights — Article 3(3) — Obligation of equal and non-discriminatory treatment of traffic — Possibility of implementing reasonable traffic management measures — Additional ‘zero tariff’ option — ‘Zero tariff’ excluded in the case of roaming)