Annegret Engel (LL.M., Ph.D.) has been working as a Lecturer in EU law at Cardiff University, School of Law & Politics (2014-2017). She holds a Ph.D. in EU Law from Durham University (2014) and has previously worked for the British Institute of International and Comparative Law in London (2008) as well as the DG Internal Market at the European Commission in Brussels (2010-2011). Her main research interests are in the field of European constitutional law with a particular focus on the delimitation of competences. In addition, she is also interested in EU external relations law, international agreements and the legal implications of Brexit.

• Introduction.- Conflicts between the Union's different types of competences.- The choice of legal instrument - a choice of legal basis?.- The choice of legislative procedure - a matter of institutional preference?.- The sui generis nature of external competences.- Conclusions.

Annegret Engel (LL.M., Ph.D.) has been working as a Lecturer in EU law at Cardiff University, School of Law & Politics (2014-2017). She holds a Ph.D. in EU Law from Durham University (2014) and has previously worked for the British Institute of International and Comparative Law in London (2008) as well as the DG Internal Market at the European Commission in Brussels (2010-2011). Her main research interests are in the field of European constitutional law with a particular focus on the delimitation of competences. In addition, she is also interested in EU external relations law, international agreements and the legal implications of Brexit.

• Introduction.- Conflicts between the Union's different types of competences.- The choice of legal instrument - a choice of legal basis?.- The choice of legislative procedure - a matter of institutional preference?.- The sui generis nature of external competences.- Conclusions.

Annegret Engel (LL.M., Ph.D.) has been working as a Lecturer in EU law at Cardiff University, School of Law & Politics (2014-2017). She holds a Ph.D. in EU Law from Durham University (2014) and has previously worked for the British Institute of International and Comparative Law in London (2008) as well as the DG Internal Market at the European Commission in Brussels (2010-2011). Her main research interests are in the field of European constitutional law with a particular focus on the delimitation of competences. In addition, she is also interested in EU external relations law, international agreements and the legal implications of Brexit.

• Introduction.- Conflicts between the Union's different types of competences.- The choice of legal instrument - a choice of legal basis?.- The choice of legislative procedure - a matter of institutional preference?.- The sui generis nature of external competences.- Conclusions.