Twenty years ago the United Nations adopted the Convention of the Rights of the Child. The CRC or UNCRC, sets out the civil, political, economic, social and cultural rights of children.
Nations that ratify the UNCRC are bound to it by international law.
As of December 2008, 193 signatories had ratified it, including every member of the UN except the US and Somalia.
|The UNCRC has been used as a blueprint for child protection legislation around the world
The treaty restricts the involvement of children in military conflicts and prohibits the sale of children, child prostitution and child pornography.
Bangladesh is a signatory to the UN pact.
However, child marriage remains a widely accepted practice.
According to a UN report, 63 per cent of all Bangladeshi girls below the age of 25 are married off before they reach the legal age of 18.
Non-governmental organisations in the country are trying implement a clause in the UNCRC to protect underage brides.
Al Jazeera's Nicolas Haque reports from Dhaka on how the simple birth certificate can help reduce the number of children forced into marriages.
The extreme cases of child marriages also include the Democratic Republic of Congo and Afghanistan.
The UNCRC generally defines a child as any human being under the age of 18, unless an earlier age of majority is recognised by a country's law.
Unicef, the UN children's agency, says early marriage constitutes a violation of a girl's human rights, primarily because it can deprive her of the right to give full and free consent to marry.
Pregnancy-related deaths are the leading cause of mortality for girls aged 15 to 19 worldwide.
While this is often linked to poor health care, the risks are increased by the physical immaturity of the girls, according to Unicef.
Despite the existence of the UNCRC, the UN estimates that one billion children are still deprived of food, shelter and clean water.
In addition, hundreds of millions more are affected by violence.
Barack Obama, the US president, has said he wants to change his country's "embarrassing" non-participation in the UNCRC.
Vitit Muntarbhorn, a former UN special envoy on the Sale of Children, Child Prostitution and Child Pornography, told Al Jazeera: "Many countries all over the world become parties but they enter with reservations not to accept various provisions."