Full Idea
Moral blame is grounded in the law of reason, which regards reason as a cause that, regardless of all the empirical conditions, could have and ought to have determined the conduct of the person to be other than it is.
Gist of Idea
Moral blame is based on reason, since a reason is a cause which should have been followed
Source
Immanuel Kant (Critique of Pure Reason [1781], B583/A555)
Book Reference
Kant,Immanuel: 'Critique of Pure Reason', ed/tr. Guyer,P /Wood,A W [CUO 1998], p.544
A Reaction
This appears to be a description of akrasia, in which case it is hard to see how a reason is a cause if it doesn't actually produce the result it judges to be right. Kant is an intellectualist about morality, but not about practical reason, it seems.