Once you have settled on a topic—and again before you publish—you need to conduct a preemption check to make sure that no one else has published on your topic or, if there are articles on your topic, that they don't have the same analysis. This means that you will need to identify, locate and scrutinize any articles that deal with your topic.
If you find an article that covers the ground you were planning to, think of ways to adjust your topic. Could you critique the other author's analysis and propose something different? Could you update the other author's work and discuss more recent developments? Could you add a different perspective, such as law and economics? Could you do a comparative piece, looking at how the issue has been addressed in another jurisdiction? (See Finding & Developing Topics.)
What counts as preemption is subjective. In general, a short newsletter article or a blog post will not preempt a full-length law review article. (If the short piece provides an insight or bit of analysis that you draw on, be sure to cite it and give credit!) An annotation in the American Law Reports series will be helpful to you in your research but ordinarily would not preempt a law review article, because law review articles are much more analytical than annotations, which organize and summarize cases.
It is very important to be aware of what already has been written in your area of interest and to engage with this literature if it’s relevant. Keep records of where you look and what you find: the research you do for the preemption check may be useful as you write your paper.