You're confused.
Tariff's are a duty imposed on imported goods by sovereign nations. As an example, Red China imposes up to a 40% tariff on some American made goods.
That's quite a difference from a global tax collected by an unelected foreign enity (the UN).
PS: Dubya has dumped Free Trade into the global garbage. Free Trade now resides along side that other Republican tenant, the minimum wage.
He done good...