there are a few differetn searches you can perform in google to find dofollow law blogs....but I would not waste my time concentrating on the whole no/do follow thing.
#1 if all you blog cooments are dofollow...this will throw up a flag with google
#2 blog comments are becoming worthless
#3 nofollow blog comments can still count as backlinks to google
google search strings for dofollow blog....just add law outside (before) the quotations
"u comment i follow"
"Enter [email protected] in the Name field to take advantage."
"This site uses KeywordLuv. Enter [email protected] in the Name field to take advantage"
"blog comments powered by Disqus"