Preemption is a prohibition on writing about a topic that has already been discussed and / or analyzed with the same approach or lens by another scholar. Duplicative scholarship is barred by academic journals. That said, if a topic has already been discussed at length, it does not mean that is it preempted. Instead, preemption merely means that the writer must develop a novel lens through which to analyze the issues. Thus, both approach and scope are iterative in nature: the initial approach selected, or the scope of the topic chosen, may require updating after conducting a preemption check.

Preemption verification is not as simple as Googling the topic by key word, nor conducting a basic search on HeinOnline. A robust preemption check should be guided by the paper's subject matter. That said, there are a few general tips and tricks for beginning the process:

1. Case, Statute, Circuit Split, and Comparative Papers

• If you are writing about a case, statute, or circuit split, you can use Westlaw and / or Lexis to view the sources that subsequently cite the focal case(s) or statute. Drill down to look at secondary sources and law reviews, specifically. 
• If you find a law review article that discusses a topic that is similar, review the sources that the author cites for the overlapping subject area. Be sure to read those sources as part of your preemption check.

• Because these tend to be time-sensitive papers, be sure to check works in progress by other academics on bePress and the Legal Scholarship Network (a division of the interdisciplinary SSRN)

2. Non-Legal Framework and New Trends Papers

• Start with the resources you already know: how did you become familiar with the topic? Use those resources to develop a roadmap for further investigation, starting with the sources that the first resource cites.
• Search full-text articles by various keyword permutations (Boolean string) on JSTOR, HeinOnline, Google Scholar, Westlaw, and / or Lexis. A helpful tip: the search algorithms favor recent scholarship, so to capture the most relevant articles by topic, be sure to adjust the date range through advanced search.
• Search for dissertations within specific institutions, academic disciplines, and by topic keyword search on ProQuest.
• As a catch-all, try various keyword permutations in legal indexes. Keep in mind that indexes do not search the full text of an article. They contain only a bibliographic record including information about the article, such as author and title, and sometimes an abstract. Access the following through the Berkeley Law Library:

Evaluate whether updating the scope would resolve the preemption, whether the paper would still be feasible, and whether it would still be of interest to you. Consider adjusting: 

1. Where (jurisdiction / geography)

2. Who (affected population)

3. What (type of lens / fieldwork applied)

4. When (time period)

Alternatively, rather than updating your scope due to preemption, you can limit the scope to the earlier scholarship by responding with an analysis précis or literature review. However, particularly for an Option 2 paper, you should confirm with your project supervisor that the "four corners" format is acceptable for developing a thesis. 

For detailed instructions about specific aspects of preemption verification:

1. UC Berkeley Law - tailoring searches by resource type

2. University of Washington Law - search permutation tips

3. University of Illinois Law - setting up alerts to stay current