I agree that you should have specified a law degree if that's what you need - as NJ says, there are thousands applying for some jobs these days. A job description/person specification with it should have clarified this when you advertised (we always include this in the spec these days, as to what is essential and what is desirable), but the person spec is often seen as the ideal candidate, and many applicants don't match up with every single criterion. I applaud your applicant for having a go.