Conference of the Religious Congregations of the Netherlands, Commission for Canon Law
since 1993 Consultant
Canon Law Society of America, Commission "Laity and Jurisdiction"
since 1994 Member of the Commission
Netherlands Catholic Bishop's Conference, work-group "sexual abuse in pastoral relationships"
1995-2001 Member of the work-group
Netherlands Catholic Bishop's Conference, work-group "Ecumenical questions"
since 1995 Member of the work-group
Netherlands Catholic Bishop's Conference, work-group "Churches and mixed marriages"
since 1999 Member of the work-group
Catholic society for ecumenics "Athanasius and Willibrord", The Netherlands
2002-2006 Member of the Board of Directors
Farfa Permanent Working Group on the Petrine Ministry
2005-2010 Member of the work-group (a mixed Lutheran / Catholic group)
Johann-Adam-Möhler-Institut für Ökumenik, Paderborn, Germany
since 2007 Member of the Advisory Board
Periodical "L'Annee canonique", Paris
since 2007 Member of the Editorial Board
World Council of Churches, Commission on Faith and Order
since 2008 Member of the Standing Commitee (as representative of the Catholic Church)
Ökumenekommission des Bistums Erfurt
2008-2014 Member of the Commission
International Journal for the Study of the Christian Church, England
since 2009 Member of the Editorial Board
ET-Studies: Journal of the European Society for Catholic Theology
since 2009 Member of the International Editorial Board
World Council of Churches, Research Group on Church Unity
since 2010 Member of the planing commitee Catholic News Agency
Pontifical Commission for the Protection of Minors
Member initially from 2018-2021