The "Private Law" Oxymoron

See Peter Spiro's story on Opinio Juris about the big retailers' (Walmart, Tesco, etc.) Global Social Compliance Program.  I had not heard of this one.  It is interesting that the retailers would join together to set standards for their suppliers.  Is it intended to take the wind out of the sails of the UN's social compact program?  Is it really going to help marketing?  Was there pressure from investor groups?  Why else would these companies do this?  If developing countries would oppose these types of measures in the WTO as possible blue protectionism, would they prefer a private initiative?