"It must also be observed, that individuals are not so perfectly free in the economy or government of their affairs as not to be subject to the laws and regulations of police made by the sovereign. For instance, if vineyards are multiplied to too great an extent in a country which is in want of corn, the sovereign may forbid the planting of the vine in fields proper for tillage; for here the public welfare and the safety of the state are concerned. When a reason of such importance requires it, the sovereign or the magistrate may oblige an individual to sell all the provisions in his possession above what are necessary for the subsistence of his family, and may fix the price he shall receive for them. The public authority may and ought to hinder monopolies, and suppress all practices tending to raise the price of provisions — to which practices the Romans applied the expressions annonam incendere, comprimere, vexare." (Vattel, at §255.)
There you have it - "annonam incendere, comprimere, vexare" (and throw in a little hocus pocus) and natural law quite naturally sanctions government regulation of the economy and government price fixing!
And that is different from what we currently have how?