Throughout the 1920s and 1930s, the League of Nations complained that of all the mandatory powers South Africa was the most delinquent with regards to observing the terms of its mandate. The Mandate Commission vetoed a number of ambitious South African policy decisions, such as proposals to nationalise South West African railways or alter the preexisting borders. Sharp criticism was also leveled at South Africa's disproportionate spending on the local white population, which the former defended as obligatory since white South West Africans were taxed the heaviest. The League adopted the argument that no one segment of any mandate's population was entitled to favourable treatment over another, and the terms under which the mandate had been granted made no provision for special obligation towards whites. It pointed out that there was little evidence of progress being made towards political self-determination; just prior to World War II South Africa and the League remained at an impasse over this dispute.