The Pan-American Conference in Montevideo passed a "Convention on the Nationality of Women" in 1933. It was passed by the Pan American Conference at the same time as the "Treaty on the Equality of Rights Between Men and Women". These were the first pieces of international law to "explicitly set sexual equality as a principle to be incorporated into national legislation" which was required of countries ratifying the convention and treaty. Lobbying by the American National Women's Party has been credited with this legislation. However, neither the International Labour Organization (ILO) nor the League of Nations passed any legislation on the issue during the interwar years.