Most associations of law firms boast about their size and international reach. The likes of TerraLex, LexMundi, Primerus and others believe that global coverage matters to clients. Other networks stress their regional expertise and footprint.
Still other networks of firms orient themselves around specialized areas of law. There are groups for employment law (See my post of March 11, 2010: Ius Laboris.) as well as for intellectual property law (See my post of April 10, 2006 # 4: Association of Patent Law Firms.) and litigation (See my post of April 15, 2011: The Network of Trial Law Firms.). It seems logical that there would be such groups, which share research, referrals, and marketing, in more areas of law, such as environmental or import/export and customs or perhaps immigration. I welcome hearing about them since I have probably simply not run across mention of them.