In general, university guidelines or policies on plagiarism are not sufficiently detailed to cope with the technical complexity of software. Software plagiarism can have a significant impact on a student's degree result, particularly in courses were there is a significant emphasis on large-scale projects. We argue that a policy for software reuse is the most explicit, and fair, way of overcoming this problem. In our policy, we specify the notion of software to cover all the documents that are generally built during the engineering of a software system -- analysis, requirements, validation, design, verification, implementation and tests. Examples are used to show acceptable and unacceptable forms of reuse, mostly at the design, testing and implementation stages. These examples are represented in Java, although they should be easily understood by anyone with software engineering experience. We conclude with a simple code of practice for reuse of software based on a file-level policy, combined with emphasis on re-using only what is rigorously verified