Do I need a law qualification?

I have worked in HR for more than nine years and my current job is in an HR shared service centre in Glasgow. I feel a bit stuck in a rut and think my lack of a specialist HR qualification (I have an MSc degree but no CIPD qualifications) may be halting my progression. I am particularly interested in employment law. I’m not sure how it would boost my career prospects and I can’t afford to study full time. Is it worthwhile for me to gain an HR qualification at this stage in my career? How do I ensure it is worth the investment of my time and money?