"Of counsel" is one of those elastic phrases that can mean almost anything. Or so it seems based on how it's used.

In fact, though, ethics opinions over the years have given the term meaning, or at least defined its outer boundaries. And what are those boundaries? When is it appropriate for a lawyer to describe himself or herself as "of counsel" to a firm?

Not for "single case affiliations and referral source schemes," writes David B. Sosin in the latest ISBA Senior Lawyers newsletter. "Similarly, the collaboration of unrelated lawyers in Of Counsel designations to expand their firm expertise on paper was not permitted" by a 1990 ABA ethics opinion.

Sosin looks at how lawyers may use the term and how they should not, and also at how the "of counsel" designation has evolved over the years. Read his article.