To ensure that the topic you select has not been preempted by another author, you will need to do a preemption check of the subject matter. The Index to Legal Periodicals is an excellent online tool for this purpose. Other possible sources to check are Hein Online, and the law review databases on Westlaw, Lexis Advance. If you plan to use these tools from home, with the exception of Westlaw and Lexis Advance, you will need to log on using your university network credentials.
Another online source of new and pre-published scholarship is SSRN. Similar to SSRN is BePress, another legal scholarship repository that is free to search. The advantage to searching both SSRN and BePress is that since they provide access to pre-publication articles and "works in progress" they act as useful preemption check services for areas of the law that are constantly changing.