The nomination of incumbent Pierre Nkurunziza to stand again for president in the 2015 national elections triggered a political and security crisis in Burundi. A crucial element in the controversy around his third term was the legality of his candidacy. This paper analyses how domestic and international actors responded to the legal loopholes that characterised Burundi’s term-limit legislation. Three responses are distinguished. First, quite paradoxically, an argument was put forward by third-term supporters that stressed constitutional legality, a value usually invoked by third-term opponents. Second, a peace agreement was referred to as a source of legitimacy and as a legal norm. Third, a Constitutional Court ruling was invoked to address the legal loophole. Despite the apparent irrelevance of legal norms in an increasingly authoritarian environment, law significantly shaped the dynamics of the third-term debate and of the wider crisis. The Burundi case also illustrates the limitations of constitutional engineering of democratic governance.