FMCSA’s International Program webpage provides resources and guidance on the regulations, Hazardous Materials regulations and safety requirements for motor carriers domiciled in the U.S., Canada, and Mexico who operate, or are applying for authority to operate, beyond their own borders to transport international freight.
The links on the webpage below provides clarification for drivers when returning across the border into Canada who have been using personal conveyance and agriculture exemptions in the US.
https://www.fmcsa.dot.gov/international-programs