Lawmakers around the country are crafting new laws to target "dark patterns" -- user interface designs that trick or coerce users into enabling cell phone location tracking, sharing browsing data, initiating automatic billing, or making whatever other choices their designers prefer. Dark patterns pose a serious problem. In their most aggressive forms, they interfere with human autonomy, undermine customers' evaluation and selection of products, and distort online markets for goods and services. Yet crafting legislation is a major challenge: Persuasion and deception are difficult to distinguish, and shifting tech trends present an ever-moving target. To address these challenges, this Article proposes leveraging state private law to define and track dark patterns as they evolve. Judge-crafted decisional law can respond quickly to new techniques, flexibly define the boundary between permissible and impermissible designs, and bolster state and federal regulatory enforcement efforts by quickly identifying those designs that most undermine user autonomy.