This chapter focuses on legitimacy of ICT standardization as a form of regulation. After reviewing the relevant scholarship on legitimacy and effectiveness of private transnational regulation, it takes up Schmidt’s framework on input, throughput, and output legitimacy as the most relevant for ICT standards. It then introduces a nonexhaustive list of procedural meta-principles through which the private regulatory regime created by ICT standardization can be legitimized. These processes are addressed in this chapter as “good governance principles” and include participation, transparency, reason-giving, and review; they also serve as procedural mechanisms to hold private regulators accountable and to ensure legitimacy of their rule-making.