no, this won't work
I just found out that the standard method of robot exclusion won't work. The problem is that all my URL's use the same directory structure, and individual articles are only identified by the parameters following the question mark ("Contributions", "Feedback", etc.). If I put in an exclude instruction, it will stop search engines from indexing the entire site.
How about, instead, a message on the top of the Contributions page saying "All work is owned solely by the individual authors and may not be used or reprinted without permission". I think that should serve the same purpose.