Neither the professor nor the librarian knew about the topic, so the librarian set out to do her initial research and found that there were no guides out there on how to research tariff bindings.
So the librarian, Mary Whisner, took it upon herself to create a research guide on tariffs and shared it with the rest of the American Association of Law Libraries community.
The University of Washington Gallagher Law Library's research guide on researching tariffs can be found here.
This is a good time to mention that librarians create research guides in nearly all areas imaginable. It's one of our main functions. So if you are having a hard time performing research on a topic, you might Google '[topic] research guide' to find a starting place for research.
For example, I had a student email me recently to ask about some initial information on how to write a case note. The student had never taken Scholarly Writing nor was he on law review. I gave him some information but also told him to Google 'case note research guide' for more information. This Google search brought up guide by Monash University.