A lawyer who has fought for reduced criminal sentences for nearly two decades has filed a long-shot class action in an attempt to mitigate thousands of harsh criminal sentences at once.

Marcia G. Shein, of Atlanta’s two-attorney Shein & Biggs, is trying to do–through civil litigation in a federal district court in Georgia–what dozens of other lawyers have failed to do in criminal proceedings: obtain a ruling that the different federal sentences for crack and powder cocaine violate the civil rights of black defendants.