The idea is that members of the Kimberley Process cannot trade with non-members.
"The Kimberley Process is not all things to all people, but that doesn't mean it is not doing a decent job, " she said.
The industry says that the introduction in 2000 of a system of certification for rough diamonds - the Kimberley Process - has improved the situation.
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Some companies may benefit more than others: for De Beers, for example, the Kimberley Process reduced a threat to the industry and if anything increased its own brand's dominance.
According to Amy Barry of Global Witness, the Kimberley Process has yet to demonstrate itself capable of stopping the trade because of a lack of political will among member states.
The ban was imposed by the Kimberley Process (KP), the international organisation that polices diamonds, following reports of large-scale killings and abuse by Zimbabwe's security forces in the Marange diamond fields.
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The Kimberley Process started when Southern African diamond-producing states met in Kimberley, South Africa, in May 2000, to discuss ways to stop the trade in conflict diamonds and ensure that diamond purchases were not funding violence.
But in a statement to the AFP news agency Mr Mvouo said the president of the Kimberley Process, which is based in Canada, had not respected the organisation's rules concerning the right to respond to allegations, mediation, and confidentiality.
On June 18th Obert Mpofu, Zimbabwe's powerful and wealthy minister of mines, told a meeting of his country's chamber of commerce that he had got a letter from the Kimberley Process demanding Mr Maguwu's immediate release if Zimbabwe were to be allowed to resume diamond trading.
Instead of the outright ban on Zimbabwe diamond sales recommended by the World Diamond Council last year, the Kimberley Process decided in November simply to suspend sales for six months to give the government another chance to comply with its standards and to withdraw all troops from the area.
Late last year a major international environmental group pulled out of the so-called Kimberley Process designed to guarantee that diamonds do not come from conflict zones.
"Kimberley Process participants need to have complete confidence that conflict diamonds are not entering the legitimate trade, " said Tim Martin, the organisation's chairman.
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