On September 11, 2009, the Premiers of Québec and Ontario signed a common market agreement (“Accord pour un marché commun”) that came into force on October 1st, 2009 with the exception of the provisions concerning regulatory cooperation that will come into force in March 2010. In regard to the environment, the agreement recognizes the right for each party to adopt different environmental standards in order to protect or improve the quality of their respective environment. Furthermore, the Ontario-Québec agreement further states explicitly that the absence of scientific certainty regarding the use of an environmental measure will not constitute a sufficient justification to consider such a measure as a violation. This appears to constitute an implied recognition of the precautionary principle. The agreement further provides for the harmonization of regulations concerning emission standards for heavy vehicles, as well as the joint development of regulations and programs concerning products stewardship and, namely, the internalization of environmental costs, eco-conception, performance objectives and traceability of recovered products.