To do a preemption check to ensure that no one else has written on the topic that you have in mind, you will want to do some thorough research. A logical way to do this is to start with the easiest full-text databases to search across many law journal articles at once. Each of these databases has a different collection of law journals, and sometimes there will be overlap. After running searches in full-text databases, you will want to search some free databases where people publish articles before they are officially published. Then you will want to search the Indexes, these databases cover a wider variety of journals, some of which will be outside of the scope of the full-text databases. Indexes largely provide you with information about the article, and usually have an abstract that will let you know whether or not the article is on your topic. If you want to see the full text of these articles, you may need to place an interlibrary loan if they are not available in the UC Law SF full-text databases.
These resources may be useful to ensure that your topic has not been written in a non-law journal, but these databases may also be useful later when you are doing research for your paper, because you may want to use knowledge (including statistics) from other disciplines to support your arguments.
If you want to be thorough in your searching, or if you are having difficulty finding relevant articles, you can try searching a journal index. Index searches are only search the title or abstract of the article, (NOT a full-text search).
Search for the by journal title in:
If you have a citation and you cannot decipher what the abbreviation means, you can use:
The Bluebook by 
Prince's Bieber Dictionary of Legal Abbreviations by 
If an article you have found is not in a law journal, and not in one of the online resources at UC Law SF, you may want to search the online databases collection at the:.