This chapter examines the ways in which the UK Parliament formally constrains the government and engages with European Union (EU) institutions. The House of Lords and the House of Commons both have processes to ensure that legislation proposed at the EU level has been properly reviewed before it takes effect in UK law. The ‘scrutiny reserve’, which stipulates that ministers should not agree to proposals under scrutiny, is used to elicit information about the government's negotiating position. Parliament also has a role in examining EU legislation and providing direct access to European institutions. The chapter first provides an overview of the EU legislative process, focusing on three principal EU institutions: member states, the European Parliament (EP), and the European Commission. It also considers the formal role of national parliaments in the EU legislative process, the UK Parliament's scrutiny of the EU legislation and its effectiveness, and parliamentary scrutiny after Brexit.