"Companies are being sold the idea that becoming a leading public thinker on some issue affecting their industry will give them a competitive edge." The Economist, April 25, 2015. Here is the article.
You position and package what you need to sell in the way the marketplace prefers. Currently, as The Economist confirms, that way is being labeled a "thought leader" in some niche. For a law firm it could be intellectual property or employment issues. Ideally, there should be multiple gurus on the subject in any one law firm.
Of course, establishing, maintaining and growing thought leadership mandate total outreach. That includes keynote speeches, opinion-editorials published in both business and legal media, being buttonholed for interviews, white papers, social media and books (yes, plural). Likely you will require more help getting that done than just your in-house marketing director. For that very reason, the public relations industry is exploding in growth.
Thought leadership is the best thing which has happened to the business of communications.