This chapter provides some of the most important existing legal principles pertaining to intelligence work and oversight. It addresses how many of these principles have been discussed in key academic and policy-oriented contributions in the field. The chapter demonstrates how the body of intelligence oversight literature has been expanded both in thematic scope and focus. It illustrates that good principles and elaborated standards have often fallen short of actually being adopted in practice. The establishment of legitimate and effective intelligence oversight mechanisms is a demanding task for any democracy. Secrecy is a necessary prerequisite for many aspects of intelligence governance, including oversight. The most obvious tool to improve oversight bodies' ability to conduct their job is to give them full access to the intelligence services' digital and analogue systems, records, installations and other properties. The chapter concludes by identifying possibilities of solutions for better oversight in the future.