Economists’ Normative Case for Government Intervention is a Very Poor Positive Theory of that Intervention
Boudreaux uses it as a title for the post, thus the capitals.
Let me unpack this as a way to figure it out for myself.
A normative case is an argument about how we think things ought to be. So the “normative case for government intervention” is a way of saying that government intervention is way to make things the way they ought to be.
A positive theory is one based on facts, about facts. So a “positive theory of that intervention” would be a theory of government intervention that incorporates and/or explains facts about the motivations and consequences of those actions.
Putting it all together, what I get out of this is that a position that the world would be a better place if only the government did something ignores the realities of what has happened when they have done some other things in the past.
I think the same could be said for parenting.