Morijn is a professor of law and politics in international relations at the University of Groningen Faculty of Law, where he holds a chair endowed by the Netherland Association for International Affairs (NGIZ). He also chairs the rule of law working group of the Meijers Committee, a Dutch NGO, and is a member of the Dutch Advisory Council on Migration and the Scientific Committee of the EU Fundamental Rights Agency. Apart from these roles, he serves as a reserve officer in the rule of law platoon in the Royal Dutch Army (Civilian-Military Action Command).

Morijn frequently briefs the Dutch and European Parliaments. He is the founding mentor of Our Rule of Law, a for-students-by-students initiative that creates opportunities for students to learn about democracy and rule of law protection in Europe. From 2009 to 2018 he served, respectively, as a senior human rights law adviser at the constitutional affairs unit of the Dutch Ministry of the Interior and Kingdom Relations and the head of unit of that same ministry at the Dutch Permanent Representation to the EU. Recently he held the position of commissioner at the Dutch National Human Rights Institute/Equality Body.

Morijn studied Dutch law in Rotterdam, The Netherlands, and EU law at the College of Europe in Bruges, Belgium, and holds a PhD in international law from the European University Institute in Florence, Italy. At SPIA, he will continue his work on democracy and rule of law protection.