In a break with historical practice, the National Labor Relations Board hasn’t heard oral arguments in major labor cases in nearly six years, but 30 labor law professors now are urging the board to return to arguments in a trio of pending cases among the most significant in the board’s 71-year history.

The three cases are known collectively as the “Kentucky River cases.” With these cases, the board is expected to decide — perhaps as early as the end of August — who is a supervisor for purposes of self-organization, collective bargaining and other labor rights under Section 7 of the National Labor Relations Act. The act excludes “supervisors” from its definition of “employee.”