Once an undergraduate student has enrolled for 12 or more hours, UI Direct will not permit the student to drop below the full time level. If it is necessary to drop a course that causes an underload, you must do so with the aid of your college office. This rules does not apply to graduate students. This rule does not apply to summer terms. I can't get into a class because it has seats reserved.
Departments can reserve seats in a class or in a section for specific groups of students.
These groups can be based on college, curriculum, class, honors, and other categories. If the timetable does not have clear notes with the course describing the seat reservations, contact the teaching department for more information. Where reservations are limited in duration, you can try later on.