Abstract: Two Articles from this volume of the Harvard Law Review propose changes in the role of federal courts. One, by Curtis Bradley and Jack Goldsmith, argues that customary international law should not be considered federal common law, despite the contrary beliefs of many international lawyers. The other, by Dan Kahan, proposes that Chevron deference be granted to the Department of Justice's interpretation of criminal statutes. In this essay, Professor Lessig argues that the two Articles have more in common than might at first appear: both Articles attempt to make a commonly accepted practice contestable, and bid to change that practice in a manner that delegates decisionmaking power to more democratically accountable actors. The proposals of both Articles follow a pattern that Professor Lessig calls the Erie-effect. In this pattern, changes in context as well as changes in the practice at issue make it possible to question the legitimacy of continuing to engage in the practice and push the issue to the foreground of public attention. This essay hopes to spark debate on the proper role of context in interpretive theory by using the lens of the Erie-effect to explore how practices are rendered contestable.