The International Labour Organization (ILO) is a specialized agency of the UN that was created in 1919.

According to the ILO website "The idea of international labour legislation arose early in the nineteenth century as a result of ethical and economic reflection on the human cost of the Industrial Revolution."

The ILO creates international labour standards called Conventions, the first of which was adopted in 1905 and was concerned with the regulation of night work for women.
In terms of child labour, the ILO has a specialized board called the International Programme on the Elimination of Child Labour (IPEC)

The ILO has made two significant Conventions that deal with Child Labour: Convention 138, adopted in 1973 and more recently, Convention 182, adopted in 1999.

Convention 138: Minimum Age Convention
First adopted in 1973, this convention recommends lowering the minimum age of employment of any kind to 15. It also recommends that people between the ages of 15 and 17 be restricted from work that is agreed to be dangerous or hazardous. C.138 is considered to be the more far-reaching of the two, calling for an end to child labour around the world. To date, it has been ratified by 134 countries.

Canada has yet to ratify this convention, along with the United States, Iran, and Singapore. There are 191 member states in the United Nations, and 57 have yet to ratify C.138.

The list of countries who have ratified Convention 138 can be found here.

Convention 182: Worst Forms of Child Labour
This convention was adopted in 1999 to focus the attention of the international community on child labour that is dangerous to a child's physical and emotional health. So far, it has been ratified by 150 member states.

Canada ratified this convention in June of 2000. There are 191 member states in the United Nations, and 41 have yet to ratify C.182.

The list of countries that have ratified Convention 182 can be found here.