I was speaking to the particular example given, where there are two popular positions on the subject held by lay people, while all expert accounts support only one of those positions. In this context, where all experts who have written on the subject have agreed with the same position, surely it is not original research to say so.
It would be easiest in this case just to state it as fact and cite the sources you've found.
"While some members of the public believe X [cite], legally, Y is correct [cite][cite][cite]."
You are allowed to assume that your sources are correct, as long as they appear reliable (something published in a law journal counts as reliable). That's why we cite sources, so in the event that the source is wrong it is clear who is at fault, and we can't be charged with libel, or whatever else the consequences of false information may be.