Their use by the state, its associates, and collaborators is nevertheless a violation of the natural law because the state outlaws competing media of exchange.
Such monetary schemes would not violate the natural law, but as Rothbard has rightly pointed out, they might nevertheless prove impossible to initiate since, according to Mises' regression theorem, all media of exchange must have their origin in a commodity that is valued in a state of barter.
This is so because the reproducer is taking advantage of (a different set of) statute laws that have outlawed competing media of exchange altogether.
This would not be the case under the original commodity-based system, where it was the government's monopoly of the mints, and not the outlawing of competing media of exchange, which constituted the violent aspect of the robbery.
Laissez Faire Banking and Circulating Media of Exchange.
Thus, the potential for counterfeiting makes a key difference here for the effects of government intervention in the issue of media of exchange.