Remember the movie, Do the Right Thing? That's pretty much what a purchasing code of conduct is for a company trying to be socially responsible. The code is a statement of ethical principles and appropriate practices that the company adheres to, and expects its suppliers and sub-contractors to adhere to as well. Socially responsible codes of conduct for purchasing often cover things like worker safety, environmental quality, child labor standards, and so on.
===
Need more information? Newspaper archives are one of the best online research tools.
