Gúbretha Caratniad ‘The false judgements of Caratnia’ is an unusual and understudied early Irish legal text. In its fullest form, it is divided into two distinct sections: a short, but complex, prologue, which establishes Caratnia as judge to Conn of the Hundred Battles; and a collection of 51 exchanges between Caratnia and Conn. The prologue describes Caratnia as a liability who would be redundant as a judge. In the second section of the text, however, Caratnia's ingenuity as a judge becomes clear. In every exchange, Caratnia begins by giving a judgement which is ostensibly incorrect; he is challenged by Conn, who accuses him of judging falsely. In each case, Caratnia proves why he is correct by citing exceptions to established legal rules. It is rare to make exceptions the focus of a text, yet the comprehensive nature of the glossing reflects a text which was used alongside the wider corpus of early Irish legal material. It is one of a handful of extant Irish law texts, such as Anfuigell and Recholl breth, to cover a broad range of topics which appear to have no connection to one another, other than being an exception to the rule. The aim of this paper is to explore Gúbretha Caratniad as a text for teaching, and, in particular, for teaching how a law student should think about the law, rather than simply know the law.