If you do a Google search with the search terms site:.edu and using inverted commas around "Fundamentals of Legal Studies" and "Fundamentals of Law" you should be able to find out which is more common. If this is the name of a module on a law degree, an alternative name for a similar module in Britain might be "Introduction to Law". I'm not sure that I would regard "fundamentals of legal studies" or "fundamentals of law" as a distinct discipline from law or legal studies in general. I don't know whether the term "legal studies" is sometimes used to mean studies which, though they include a legal element, are not full-on law studies - for example, could a course on "legal studies" have a heavy element of criminology, penology, philosophy of law or similar?