Jens is a Professor of Comparative Law and Director of International Strategy and Partnerships at the University of Cambridge, where he also is the Director of Cambridge Family Law. He also is a Director of Studies at and Fellow of Gonville and Caius College (Cambridge), Cheng Yu Tung Visiting Professor at the University of Hong Kong, Honorary Professor at the University of Aalborg and Extraordinary Professor at the University of the Western Cape in South Africa. He also is an Honorary Fellow of St. John's College/Hong Kong and an Academic Door Tenant at Queen Elizabeth Building, London. Jens has held visiting positions in Sydney, Auckland, London, Vienna, Leuven, Barcelona, Padua, Louvain-la-Neuve and Melbourne.

His publications include major comparative studies on the legal status of transgender and transsexual persons (2004 and 2015) and the legal status of intersex persons (2018), as well as on cohabitation (2005), same-sex relationships (2000), matrimonial property and marital agreements (2012), registered partnerships (2017) and on ‘Eastern and Western Perspectives on Surrogacy’ (2019). In 2016 he also edited a four-volume book set on European Family Law, including a monograph on ‘The Present and Future of European Family Law'.