This paper describes a contrastive case study carried out with a sample of second-year undergraduate students studying a BA in Translation at the University of Westminster (UoW). The case study analyses the translation strategies used by translation students when dealing with certain phraseological units (PU) in a piece of legal translation coursework involving the English into Spanish language pair. This paper aims to describe the type of errors students tend to make when they translate PU in a semi-specialized legal text and to establish a comparison between the most common errors made by English native speakers (ENS) and Spanish native speakers (SNS). Under the umbrella term of phraseological unit, the stress of this study is mainly put on the analysis of collocations, which can be defined as the combination of two or more words which frequently appear in combination with each other and where each lexical unit retains its meaning (Buendía 2013; Buendía, Montero & Faber 2014). In the light of this analysis and in line with recent case studies undertaken in the field of legal translation (Pontrandolfo 2016), this paper points to some approaches that enhance the phraseological competence required in semi-specialized legal translation courses. These approaches include task-based approaches applied to translator training (e.g. Hurtado Albir 1999/2003, 2015a, 2015b; González Davies 2004; Borja 2007/2015; Huc-Hepher & Huertas Barros 2016), critical discourse analysis (Way 2012), and approaches based on decision making and problem solving (Prieto Ramos 2014; Way 2014).