SEO strategies change on a near monthly basis. Chasing Google's standards is more than a full-time job, and what works at the beginning of the year very well may not do anything by the end.
That seems to be the case with one strategy that was sometimes used to build links: guest blogging. The basic ideas was to write content that was then published on other blogs, with links included within the post back to the main firm website.
But that option is about done. Straight from the mouth of Google's SEO chief:
So stick a fork in it: guest blogging is done; it’s just gotten too spammy. In general I wouldn’t recommend accepting a guest blog post unless you are willing to vouch for someone personally or know them well. Likewise, I wouldn’t recommend relying on guest posting, guest blogging sites, or guest blogging SEO as a linkbuilding strategy.
Make no mistake: useful, original legal content writing remains the best way to naturally improve one's online presence. However, you should add that content on your own blog--not one run by others.