You should start your research in secondary sources. They guide you to the applicable treaties, custom, and general principles in your topic.
Books & Book Chapters (and e-books and e-book chapters): best quality! Books have toughest barriers to publication.
You should start your search with keywords and then find the subject headings that apply to the best results of your keyword search. But, for fun, below is a non-exhaustive list of subject headings related to human rights:
Some paper topics may require interdisciplinary research. UMN libraries have hundreds of databases, below are some examples: