English medium instruction : modelling the role of the native speaker in a lingua franca context$nElektronische Ressource Zusammenfassung: In line with the ongoing internationalisation of academia English medium instruction (EMI) in Higher Education is becoming increasingly popular in Europe. Based on an ethnographic case study of an English taught Master’s programme at a German university this dissertation assesses the role of the native speaker (both as participant and as abstract norm provider) in an EMI community of practice identifies generic challenges of EMI and provides practical recommendations for EMI quality management