The two documents you will create each do very different types of persuasion. The internal memo needs to persuade the committee that your outlines of the university’s legal obligations are accurate and complete. You’ll do that both by writing clearly and by showing that your sources are reliable.
The policy itself needs to do a different type of persuasion: It needs to persuade people that they shouldn’t use the university’s network to illegally share pirated content. There are multiple strategies available: You could simply threaten infringing users with loss of network privileges. You could appeal to their ethical side by discussing the impact of piracy on musicians, filmmakers, or programmers. You could point out that the volume of content being shared on the network is negatively impacting students trying to do coursework. A successful policy will probably use a mix of strategies.
Your primary audience (students) may tend to be very much in favor of file sharing. Students at most universities are among the most common users of file sharing to download music and movies (and students at your school are no exception). You’ll need to convince them that following the policy is a good idea.