I haven't done any out of Country consulting (to date), but I'm sure you'd be exempt from "our" Federal and Provincial taxes. As for income tax, if he's a consultant that could be deemed an employee, you may be required to holdback a remittance to your State? That can be easily checked by you by calling your local remittance office.
You might want to consider paying him in Canadian dollars too?
I did have an income source from an American company once and they did not pay any of our Provincial or Federal taxes.
Cheers,