I am doing my LLM next year in the US. I am interested in international law (arbitration, but also the relationship between human rights and business/social responsibility). I love learning, and it's a dream of mine to get a PhD... But I'm scared it will limit my chances of employment in private practice/international organizations.

I just want to know -- what is the value of having a PhD in law (specifically, if you're not sure you want to do academia)?

True. I worked for a short time as a solicitor and I've seen maybe two or three people in private practice in with a PhD in law but it definitely is the exception rather than the rule. 90% of UK qualified solicitors have just an LLB/BA even at the most elite firms. However, many German-qualified attorneys have the title "Dr.", even though it is not a prerequisite for qualification in Germany.
I am trying to move into law and development at the moment - having completed a Masters in International Development, and I'm about to embark on an LLM in International Law. I have seen a few people knocking around with SJDs and PhDs. I have been told that as an institution, World Bank really like PhDs. And two of the people I am in contact with who have worked/working as Rule of Law Advisers for WB have these terminal degrees. I know some World Bank YPP people who have PhDs too.