If this is based in such an American law then said American law needs to be changed or repealed outright.
The U.S. in 1990 passed Public Law 101-246, which focused on authorizing appropriations for fiscal 1990 and 1991 for the Department of State. Section 414 of the bill highlighted concerns over the inclusion of the Palestine Liberation Organization (PLO) in the United Nations and specialized agencies.
The section states, "No funds authorized to be appropriated from this act or any other Act shall be available for the United Nations or any specialized agency thereof which accords the Palestine Liberation Organization the same standing as member states."
It seems this law can be bypassed by any new appropriation bills by single majorities in both Houses.