Editor International Herald Tribune Paris Sir: Regarding Richard Gardner's piece Why UN Dues Aren't Optional (IHT, March 11,.p. 8), may I suggest that Mr. Gardner, for whom I have great respect, omits the governing reason why Congress is obligated to pay the US's UN dues. It is true that Article 1, Section 8, paragraph 18 of the Constitution delegates to Congress all legislative authority on a wide -- if limited -- variety of matters (the limitations of which neither Congress nor the Supreme Court any longer seem to pay much attention), with all revenue bills (presumably including payments to the UN) to originate in the House under Section 7. I do not have at hand any text from which to cite controlling Court decisions, but when I studied Constitutional Law we were told that the Supreme Court had consistently ruled that the treaty-making authority contained in Article II, Section 2, paragraph 1 of the Constitution, superseded any other provision of the Constitution with which it might be in conflict. Our law professor granted that this could theoretically result in some bizarre circumstances. The US could negotiate and the Senate approve a treaty making Elizabeth II and her heirs President of the United States for life, overriding Article II, Section 1, paragraph 3 -- reversing the results of the War of Independence. But reason suggests that the President would never negotiate such a treaty, or any other containing such an outrageous provision. Nor that the Senate would ratify it. Nor that the people would elect any senator with sentiments suggesting he might vote for such. But the UN Charter, including the US obligation to pay our share of its operating expenses (subject to renegotiation from time to time under the provisions of the Charter), was negotiated by the Executive Branch and freely ratified by the Senate after extended discussion, and has thus become an obligation of the United States as binding as any provision of the Constitution. David Timmins - Geneva