In recognition of their shared heritage and culture, Commonwealth countries are not considered to be "foreign" to each other. When engaging bilaterally with one another, Commonwealth governments exchange High Commissioners instead of ambassadors. Between two Commonwealth realms, they represent the Head of Government rather than the Head of State. Outside of bilateralism, but some Commonwealth states consider other members to be foreign for certain purposes. For example, the High Court of Australia ruled, in Sue v Hill, that the United Kingdom is a foreign power for the purpose of Section 44 of the constitution of Australia.
In addition, some members treat resident citizens of other Commonwealth countries preferentially to citizens of non-Commonwealth countries. Britain and several others, mostly in the Caribbean, grant the right to vote to Commonwealth citizens who reside in those countries. Some states, such as Canada and New Zealand, have abolished such preferences. In non-Commonwealth countries in which their own country is not represented, Commonwealth citizens may seek consular assistance at the British embassy.
The criteria for membership of the Commonwealth of Nations have developed over time from a series of separate documents. The Statute of Westminster 1931, as a fundamental founding document of the organisation, laid out that membership required dominionhood. The 1949 London Declaration ended this, allowing republican and indigenous monarchic members on the condition that they recognised the British monarch as the "Head of the Commonwealth". In the wake of the wave of decolonisation in the 1960s, these constitutional principles were augmented by political, economic, and social principles. The first of these was set out in 1961, when it was decided that respect for racial equality would be a requirement for membership, leading directly to the withdrawal of South Africa's re-application (which they were required to make under the formula of the London Declaration upon becoming a republic). The 14 points of the 1971 Singapore Declaration dedicated all members to the principles of world peace, liberty, human rights, equality, and free trade.
These criteria were unenforceable for two decades, until, in 1991, the Harare Declaration was issued, dedicating the leaders to applying the Singapore principles to the completion of decolonisation, the end of the Cold War, and the end of apartheid in South Africa. The mechanisms by which these principles would be applied were created, and the manner clarified, by the 1995 Millbrook Commonwealth Action Programme, which created the Commonwealth Ministerial Action Group (CMAG), which has the power to rule on whether members meet the requirements for membership under the Harare Declaration. Also in 1995, an Inter-Governmental Group was created to finalise and codify the full requirements for membership. Upon reporting in 1997, as adopted under the Edinburgh Declaration, the Inter-Governmental Group ruled that any future members would have to have a direct constitutional link with an existing member.
In addition to this new rule, the former rules were consolidated into a single document. These requirements are that members must accept and comply with the Harare principles, be fully sovereign states, recognise the monarch of the Commonwealth realms as the Head of the Commonwealth, accept the English language as the means of Commonwealth communication, and respect the wishes of the general population with regard to Commonwealth membership. These requirements had undergone review, and a report on potential amendments was presented by the Committee on Commonwealth Membership at the 2007 Commonwealth Heads of Government Meeting. New members were not admitted at this meeting, though applications for admission were considered at the 2009 CHOGM.
New members must "as a general rule" have a direct constitutional link to an existing member. In most cases, this is due to being a former colony of the United Kingdom, but some have links to other countries, either exclusively or more directly (e.g. Samoa to New Zealand, Papua New Guinea to Australia, and Namibia to South Africa). The first member to be admitted without having any constitutional link to the British Empire or a Commonwealth member was Mozambique, a former Portuguese colony, in 1995 following its first democratic elections and South Africa's re-admission in 1994. Mozambique's controversial entry led to the Edinburgh Declaration and the current membership guidelines. In 2009, Rwanda became the second Commonwealth member admitted not to have any such constitutional links. It was a Belgian trust territory that had been a German colony until World War I. Consideration for its admission was considered an "exceptional circumstance" by the Commonwealth Secretariat.
The Commonwealth comprises 53 countries (including one currently suspended member), across all six inhabited continents. The members have a combined population of 2.1 billion people, almost a third of the world population, of which 1.17 billion live in India and 94% live in Asia and Africa combined. After India, the next-largest Commonwealth countries by population are Pakistan (180 million), Nigeria (170 million), Bangladesh (156 million), the United Kingdom (63 million) and South Africa (52 million). Tuvalu is the smallest member, with about 10,000 people.
The land area of the Commonwealth nations is about 31,500,000 km2 (12,200,000 sq mi), or about 21% of the total world land area. The three largest Commonwealth nations by area are Canada at 9,984,670 km2 (3,855,100 sq mi), Australia at 7,617,930 km2 (2,941,300 sq mi), and India at 3,287,263 km2 (1,269,219 sq mi). The Commonwealth members have a combined gross domestic product of over $9 trillion, 78% of which is accounted for by the four largest economies: United Kingdom ($2.4 trillion), Canada ($1.8 trillion), India ($1.8 trillion) and Australia ($1.5 trillion).
The status of "Member in Arrears" is used to denote those that are in arrears in paying subscription dues. The status was originally known as "special membership", but was renamed on the Committee on Commonwealth Membership's recommendation. There are currently no Members in Arrears. The most recent Member in Arrears, Nauru, returned to full membership in June 2011. Nauru has alternated between special and full membership since joining the Commonwealth, depending on its financial situation.
In 1997 the Commonwealth Heads of Government agreed that in order to become a member of the Commonwealth, an applicant country should, as a rule, have had a constitutional association with an existing Commonwealth member; that it should comply with Commonwealth values, principles and priorities as set out in the Harare Declaration; and that it should accept Commonwealth norms and conventions.
South Sudan is currently (2013) the only country specifically expressing an interest in joining the Commonwealth. Some commentators have suggested that Israel and Palestine have considered applying for membership, but there has been no formal approach."
Other eligible applicants could be any of the remaining inhabited British overseas territories, Crown dependencies, Australian external territories and Associated States of New Zealand if they become fully independent. Many such jurisdictions are already directly represented within the Commonwealth, particularly through the Commonwealth Family. There are also former British possessions that have not become independent, for example, Hong Kong, which still participates in some of the institutions within the Commonwealth Family. All three Crown dependencies regard the existing situation as unsatisfactory and have lobbied for change. The States of Jersey have called on the UK Foreign Secretary to request that the Commonwealth Heads of Government "consider granting associate membership to Jersey and the other Crown Dependencies as well as any other territories at a similarly advanced stage of autonomy". Jersey has proposed that it be accorded "self-representation in all Commonwealth meetings; full participation in debates and procedures, with a right to speak where relevant and the opportunity to enter into discussions with those who are full members; and no right to vote in the Ministerial or Heads of Government meetings, which is reserved for full members". The States of Guernsey and the Government of the Isle of Man have made calls of a similar nature for a more integrated relationship with the Commonwealth, including more direct representation and enhanced participation in Commonwealth organisations and meetings, including Commonwealth Heads of Government Meetings. The Chief Minister of the Isle of Man has said: "A closer connection with the Commonwealth itself would be a welcome further development of the Island’s international relationships"
At the time of the Suez Crisis in 1956, in the face of colonial unrest and international tensions, French Prime Minister Guy Mollet proposed to British Prime Minister Anthony Eden that their two countries be joined in a "union". When that proposal was turned down, Mollet suggested that France be allowed to join the Commonwealth, with "a common citizenship arrangement on the Irish basis." In 1957, after both proposals had been rejected, France signed the Treaty of Rome with West Germany and the other founding nations of the Common Market, later to become the European Union (EU), which the United Kingdom joined in 1973. The other European members of the Commonwealth (Malta and Cyprus) joined the EU in 2004.
In recent years, the Commonwealth has suspended several members "from the Councils of the Commonwealth" for "serious or persistent violations" of the Harare Declaration, particularly in abrogating their responsibility to have democratic government. This is done by the Commonwealth Ministerial Action Group (CMAG), which meets regularly to address potential breaches of the Harare Declaration. Suspended members are not represented at meetings of Commonwealth leaders and ministers, although they remain members of the organisation. Currently, there is one suspended member, Fiji.
Nigeria was suspended between 11 November 1995 and 29 May 1999, following its execution of Ken Saro-Wiwa on the eve of the 1995 CHOGM. Pakistan was the second country to be suspended, on 18 October 1999, following the military coup by Pervez Musharraf. The Commonwealth's longest suspension came to an end on 22 May 2004, when Pakistan's suspension was lifted following the restoration of the country's constitution. Pakistan was suspended for a second time, far more briefly, for six months from 22 November 2007, when Musharraf called a state of emergency. Zimbabwe was suspended in 2002 over concerns regarding the electoral and land reform policies of Robert Mugabe's ZANU-PF government, before it withdrew from the organisation in 2003.