From the Great Wall of China to the Berlin Wall, border walls have long served as symbols of visible, fortified manifestations of sovereign control. Increasingly, however, prosperous countries utilize sophisticated legal tools to restrict mobility by detaching the border and its migration control functions from a fixed territorial marker, creating a new framework: the shifting border. This shifting border, unlike a reinforced physical barrier, is not fixed in time and place. It relies on law’s admission gates rather than a specific frontier location. The remarkable development of recent years is that the border itself has become a moving barrier, an unmoored legal construct. These dramatic transformations unsettle ideas about waning sovereignty just as they illustrate the limits of the push toward border-fortification. By charting the logic of a new cartography of borders and membership boundaries, Professor Shachar shows both the tremendous creativity and risk attached to these new legal innovations and the public powers they invigorate and propagate. This Article further demonstrates that debates about migration and globalization can no longer revolve around the dichotomy between open versus closed borders. As an alternative to these established theoretical poles and as part of a broader attempt to overcome policy deadlocks at the domestic and international level, Professor Shachar proposes a new approach to human mobility and access to membership in a world marred by unequal opportunities for protection and migration.