I am waiting for the first guy with a blue helmut who shows up here to collect a UN Tax. The only thing left on the ground will be his socks.
The Solzhenitsyn Solution:
“And how we burned in the camps later, thinking: What would things have been like if every Security operative, when he went out at night to make an arrest, had been uncertain whether he would return alive and had to say good-bye to his family? Or if, during periods of mass arrests, as for example in Leningrad, when they arrested a quarter of the entire city, people had not simply sat there in their lairs, paling with terror at every bang of the downstairs door and at every step on the staircase, but had understood they had nothing left to lose and had boldly set up in the downstairs hall an ambush of half a dozen people with axes, hammers, pokers, or whatever else was at hand?... The Organs would very quickly have suffered a shortage of officers and transport and, notwithstanding all of Stalin's thirst, the cursed machine would have ground to a halt! If...if...We didn't love freedom enough. And even more – we had no awareness of the real situation.... We purely and simply deserved everything that happened afterward.” — Alexandr Solzhenitsyn
That's not how it will happen. Your no-longer-representative government will collect it through the IRS, after either a treaty is implemented, or a dictatorial president signs an unratified treaty but tries to pretend it is law because it hasn't been rejected by Congress.
Like gun restrictions, this sort of a UN directive can only be implemented on stable, well-controlled populations. Try collecting taxes or weapons from warlords or citizens in the Middle East or Africa.