Law often blocks sensitive personal information to prevent discrimination. It does so, however, without a theory or framework to determine when doing so is warranted. As a result, these measures produce mixed results. This article offers a theoretical framework for determining, with a view of preventing discrimination, when personal information should flow and when it should not. It examines the relationship between precluded personal information, such as race, and the proxies for precluded information, such as names and zip codes. It proposes that the success of these measures depends on what types of proxies exist for the information blocked and it explores in which situations those proxies should also be blocked. This framework predicts the effectiveness of antidiscriminatory information rules and offers the potential of a wider protection to minorities.