Commonwealth of Nations membership criteria are the corpus of requirements that members and prospective members must meet to be allowed to participate in the Commonwealth of Nations. The criteria have been altered by a series of documents issued over the past seventy-five years. The most important of these documents were the Statute of Westminster 1931, the London Declaration 1949, the Singapore Declaration 1971, the Harare Declaration 1991, the Millbrook Commonwealth Action Programme 1995, and the Edinburgh Declaration 1997. New members of the Commonwealth must abide by certain criteria that arose from these documents, the most important of which are the Harare principles and the Edinburgh criteria. The Harare principles require all members of the Commonwealth, old and new, to abide by certain political principles, including democracy and respect for human rights. These can be enforced upon current members, who may be suspended or expelled for failure to abide by them. To date, Fiji, Nigeria, Pakistan, and Zimbabwe have been suspended on these grounds; Zimbabwe later withdrew over its consistent non-compliance.