Oh, that's a good point. Rothbard and Hoppe were right to differ from Mises on the ground-basis for their arguments. Mises' outright rejection of natural law arguments in favor of rationalist (and yet also irratianalist!) ones is, IMO, a major flaw.

Nevertheless, you'll find sprinklings of natural law type sensibilites--unavoidable, I think--in his _Socialism: An Economic and Sociological Analysis_ in passages such as this one--which is the one I had in mind for the paraphrase above:

> So far as Feminism seeks to adjust the legal position of woman to that of man, so far as it seeks to offer her legal and economic freedom to develop and act in accordance with her inclinations, desires, and economic circumstances—so far it is nothing more than a branch of the great liberal movement, which advocates peaceful and free evolution. When, going beyond this, it attacks the institutions of social life under the impression that it will thus be able to remove the natural barriers, it is a spiritual child of Socialism. _For it is a characteristic of Socialism to discover in social institutions the origin of unalterable facts of nature, and to endeavour, by reforming these institutions, to reform nature_.