Free market reforms do not forbid taxes on natural resource extraction. The U.S. has plenty of such taxes, and they score very highly on measures of economic freedom.
Some of those conditions involves avoiding any sort of export tariffs and using the declared value of goods to calculate profits (ex: if I spent 20$ extracting copper, and sold it for 20$ to an overseas company which totally isn't related to me, then the taxable profit in your country is 0$).