In ‘Excusing Mistakes of Law’, Gideon Yaffe sets out to ‘vindicate’ the claim ‘that
mistakes of law never excuse’ by ‘identifying the truth that is groped for but not
grasped by those who assert that ignorance of law is no excuse’. Yaffe does not offer
a defence of the claim that mistakes of law never excuse. That claim, Yaffe argues,
is false. Yaffe’s article is, rather, an effort to assess what plausible thought might be
behind the idea that mistakes of law often should not excuse. (Yaffe is interested in
more than just the descriptive claim that in Anglo-American legal jurisdictions mistakes
of law routinely do not, in fact, excuse.) More particularly, Yaffe is interested
in what plausible normative justification there might be for this asymmetric pattern:
Asymmetry: False beliefs about non-legal facts often excuse, but false beliefs
about the law rarely excuse.
Yaffe offers a complex argument in support of Asymmetry. This paper is organised
around my reconstruction of Yaffe’s argument. I argue that Yaffe’s argument
does not succeed, but that his argument provides a template for an argument
that could succeed.