(Series Information) European Papers - A Journal on Law and Integration, 2021 6(1), 239-268 | Article | (Table of Contents) I. Introduction. - II. The European Parliament: a lobbying target sui generis? - II.1. Specificities of lobbying in the EU. - II.2. Specificities of lobbying in the European Parliament. - III. The place of EP lobbying in EU primary law and EU parliamentary law. - III.1. The TEU and the TFEU. - III.2. The Charter of Fundamental Rights of the European Union. - III.3. The EP's Rules of procedure. - III.4. The Joint Transparency Register. - III.5. The Agreement on a Mandatory Transparency Register. - IV. Evaluating lobby regulation in the EP from the perspective of EU primary law. - IV.1. Transparency as the main driver of lobby regulation. - IV.2. A troubling neglect of equality. - IV.3. Transparency as a proof of integrity? - V. Conclusion. | (Abstract) Citizens' perception that lawmaking is dominated by special interests undermines their trust in democratic institutions and lawmaking processes. This also applies to the EU, where lobby regulation remains weak despite past lobbying scandals. While the European Commission and the European Parliament established a Joint Transparency Register in 2011, registration remains voluntary for lobbyists. Given that domestic lobbies have increasingly been oriented towards the European supranational realm, adopting effective lobby regulation at EU level has become more essential than ever to protect the democratic legitimacy of EU lawmaking. This especially applies to the European Parliament, which has important decision-making powers in the context of the ordinary legislative procedure, and which represents the citizens of the EU, thereby constituting a key lobbying target. My goal, in this Article, is to show why and how lobbying should be further regulated in the European Parliament. I first examine the specificities of lobbying in the EU and in its Parliament, before looking at the EU's constitutional framework, as well as EU parliamentary law, the Joint Transparency Register established in 2011, and the provisional version of the Agreement on a Mandatory Transparency Register published in December 2020. I then evaluate the European Parliament's current regulation of lobbying from the perspective of EU primary law. I argue that its narrow focus on transparency is misguided and neglects other fundamental democratic values, such as equality. Moreover, the existing framework does not sufficiently focus on MEPs' duties of integrity.