A majority of U.S. states have established a "Seal of Biliteracy" (SoBL) to recognize students' multilingualism. Primarily under the purview of bilingual and world language education, the field of literacy research has remained largely silent on these seals. Yet, the authority these seals grant to state institutions for credentialing literacy has substantial implications for literacy research. This study analyzes 23 states that established a SoBL through legislative action. Informed by the study of seals as an ancient literacy practice, we draw on policy and visual discourse analysis to analyze state laws alongside the visual seals themselves. Incorporating theories of whiteness as property, we examine dynamics of racial, linguistic, and educational privilege to put forth a framework of biliteracy as property. Although we laud the growing popularity of the SoBL, we also caution against ceding authority to the state to assess, award, and "authenticate" biliteracy as a form of property.