These documents set out sections 91, 92, 92A, and 121 of the Canadian Constitution. Sections 91 and 92 set out the division of powers between the federal and provincial governments. Section 121 provides for free inter-provincial trade.
From the website: "The Agreement on Internal Trade (AIT) is an intergovernmental trade agreement signed by Canadian First Ministers that came into force in 1995. Its purpose is to reduce and eliminate, to the extent possible, barriers to the freeā¦