The challenge posed by legal indeterminacy to legal legitimacy has generally been considered
from points of view internal to the law and its application. But what becomes of legal legitimacy
when the legal status of a given norm is itself a matter of contestation? This article, the first
extended scholarly treatment of the International Holocaust Remembrance Alliance (IHRA)’s
new definition of antisemitism, pursues this question by examining recent applications of the
IHRA definition within the UK following its adoption by the British government in 2016. Instead
of focusing on this definition’s substantive content, I show how the document reaches beyond its
self-described status as a “non-legally binding working definition” and comes to function as what
I call a quasi-law, in which capacity it exercises the de facto authority of the law, without having
acquired legal legitimacy. Broadly, this work elucidates the role of speech codes in restricting
freedom of expression within liberal states
