What is the ruling on a student who has not paid the tuition fees for the current semester because he stopped studying and left the university?

Paying tuition fees depends on the university's registration system and the terms of the contract with it. If the fees become due upon registration or reserving a seat, then they must be paid even if the student discontinues their studies. However, if they are not due except through attendance and study, then they are only obligatory to the extent of the student's attendance and study.