In the summer of 1970 Turkey’s political polarization entered a new phase. After the radical labor union DİSK went on strike and brought Turkey’s largest cities to a standstill, the Army declared martial law and tried 260 civilians in military courts. Six months later the Army forced the government to step down, declared martial law again, and amended the Constitution in order to establish permanent half-military state security courts. The jurisdiction of these courts became the main bone of contention between leftists and the Army over the following decade. While thousands of dissidents were put on trial, attorneys, law professors and even judges linked up with labor unions to mobilize a wide resistance movement. By drawing public attention to the torture of defendants, protesting trial procedures, and in many cases persuading judges to recuse themselves, the movement rendered the state security courts useless and eventually succeeded in shutting them down through a narrow ruling of the Constitutional Court. Scholars have long debated the boundaries of cause lawyering. The debate has usually revolved around the extent to which lawyers can violate professional ideals of ‟disinterestedness” without losing the support of their peers. Taking legal activism in 1970s Turkey as my case, I argue that the distinction between ‟conventional” and ‟cause” lawyering is a political issue in its own right. Instead of treating professionalism as an a priori baseline, I see lawyering as an essentially ambiguous ideal subject to continuous contestation within a field of ‟law” broadly defined. Drawing on archival trial documentation, mainstream and underground publications, as well as legal memos between activist lawyers, I show how the issue of court jurisdiction took the shape of a conflict over the professional jurisdiction of legal experts vis-à-vis political authority. Universities, bar associations, and a broader public took part in contesting the conceptual boundaries of lawyering through ‟knowledge claims” over issues such as when lawyers can make public statements, who has the authority to evaluate the political content of a publication, and what constitutes a professional secret. The conflict caused permanent divisions among Turkish lawyers, each faction defending its version of professionalism as true ‟conventional” lawyering.