Yes, because you can always relinquish your citizenship and leave the country if you don't want to pay taxes. It should be noted that all "voluntary" market transactions occur pursuant to the implicit threat of force. When I buy something, I reserve the right to invoke the state's use of force if the product is say defective, while the seller reserves the right to invoke the state's use of force if my payment is say counterfeit currency. Per your definition, there are no voluntary transactions in any country with even the most basic government. Which is certainly a self-consistent definition, though it's arguably not that useful unless you believe that full-fledged anarchy is feasible.