Demirel completed his Master's degree and PhD in Public Law at the University of Münster, and worked as a faculty member at Dicle University Faculty of Law and Doğuş University Faculty of Law. He obtained his associate professorship and professorship at Fatih Sultan Mehmet University Faculty of Law. Demirel has held the title of Professor since 2012.
Demirel has published many articles, papers and book chapters in the fields of international law, UN law, law of attorneys, law of foreigners and constitutional law.
Since 2017, Demirel has served as the Dean of Fatih Sultan Mehmet Vakıf University Faculty of Law, as well as the Director of Fatih Sultan Mehmet Vakıf University International Law Application and Research Center, and has also taught International Law courses.
Since 2024, Demirel has been the Dean of Recep Tayyip Erdoğan University Faculty of Law and has been teaching International Law courses.