In this study we examine how university plagiarism policies interact with international graduate students' academic writing in English as they develop identities as authors and students. The study is informed by the sociocultural theoretical perspective [Vygotsky, L. (1978). "Mind in society: The development of higher mental processes." Cambridge, MA: Harvard University Press. Wertsch, J. V. (1991). "Voices of the mind: A sociocultural approach to mediated action." Cambridge, MA: Harvard University Press.] that foregrounds the crucial role of appropriation in learning, and the Bakhtinian dialogism [Bakhtin, M. M. (1981). "The dialogic imagination." Austin, TX: University of Texas Press; Bakhtin, M. M. (1986). "Speech genres and other late essays." Austin, TX: University of Texas Press.] that highlights intertextuality as a fundamental feature of language use. Relying on multiple data sources including text-based interviews, in-depth interviews with students and disciplinary professors, course syllabi, field notes, and institutional documents, we consider the social discourses that surround students as they interact with prior sources in order to understand how they construct their texts. We discuss how university plagiarism policies frame the professor-student relationship and influence student text production. We conclude by critiquing university plagiarism policies that serve to mystify academic writing, negatively affecting those students who are less familiar with the genre of academic writing.