The university is discriminating against “Students for Cannabis Policy Reform Group” because it disapproves of their message:
Considerable research indicates the use of cannabis does not contribute to healthy decision-making, particularly in college-age populations. Given the above, the University determined that recognizing the “Students for Cannabis Policy Reform Group” as a DePaul student organization would not be congruent with our institutional goals regarding the health and well-being of our students.
Eugene Volokh has details.