Taxing to exist is call a capitation tax or poll tax. It's perfectly legal in many jurisdiction and even explicitly permitted in the U.S. Constitution. Though,

Taxing to exist is call a capitation tax or poll tax. It's perfectly legal in many jurisdiction and even explicitly permitted in the U.S. Constitution. Though, penalties for inability to pay such a tax might run afoul of Substantive Due Process rights, constitute a Cruel and Unusual Punishment, or some similar open-ended clause; likewise for foreign constitutions.