Administrative law is the poor relation of public law; the hard-working, unglamorous cousin laboring in the shadow of constitutional law. Constitutional law, it is generally believed, resolves the great issues of state and society, while administrative law, in its best moments, merely refi nes those principles for dealing with the administrative state. Law students fl ock to constitutional law classes, of which most law schools have three or four in the curriculum. The same students enroll in administrative law with a sense of obligation, as if the subject is a chore one has to manage. The two fi elds are, of course, intimately related, and share an overarching purpose of managing the relationship between state and citizen, with an emphasis on protection of the latter in democratic states. On the other hand, the fi elds refl ect diff erent legal sources and modalities. In some countries, they are adjudicated by entirely diff erent courts. While constitutional law is becoming ever more comparative, with judges regularly citing each other's opinions, administrative law remains bound to the nation state. This chapter makes three arguments. First, it argues that the conceptual division between administrative and constitutional law is quite porous, and that along many dimensions, administrative law can be considered more constitutional in character than constitutions. Second, it shows that written constitutions do relatively little to legally constrain the administrative state. Rather, their role is to establish the broader structural apparatus of governance and accountability, in which the bureaucracy is the great unspoken. This leaves administrative law as a relatively free-standing fi eld characterized by great fl exibility and endurance, features that are usually thought to be more embodied in constitutions. Third, the chapter concludes that the exercise of comparison helps to expose the limits of written constitutions, and to call for greater attention to comparative administrative law as a feature of the unwritten constitution of nation states.