Speaking as a librarian, you’re a mistaken. It is actually incredibly difficult for most people to know how to verify that a source both exists and says what your unreliable informant claims they say.

Meanwhile medium sized & large law firms have their own librarians (at least in the US), and in many places lawyers from smaller firms have access to some kind of outsourced research service. The easiest solution in the world is to ask the expert researchers whose cost is billable to the client.