For pleasure craft, it's not mandatory to have one onboard, but as others have said if you have one you need an ROC-M or ROC-MC to talk on there (Industry Canada regulation). Thus there's no ticketable offense for not having a VHF on a pleasure craft, even though it's a great thing to have onboard. However, there is a catch-all ticket they can write under the Small Vessel Regulations sec. 201 for "failing to take all reasonable steps to ensure the safety of all those onboard". They being the RCMP, Municipal Police, CO Service, Parks Rangers in a BC Park, DFO Fishery Officers,- but not Coast Guard- Coast Guard don't have enforcement power for any boating safety items, just for failing to respond to pollution incident- i.e. you spill diesel and don't report it or don't try to mop it up with spill pads/boom, and it's not the search and rescue guys who would ticket for that).
So if the RCMP find you say 10 miles offshore in an open tinny and no communication device onboard and other things that lead them to believe you don't care for the safety of those onboard, they could write that catch all ticket and direct you back to shore.
For commercial it is mandatory to have a VHF onboard. Commercial regs state:
Every vessel shall be equipped with one non-portable VHF radiotelephone if the ship is of closed construction, more than 8 metres in length or carrying passengers engaged on a voyage of which any part is in a VHF coverage area, or is more than five miles from shore, or is a tow-boat.
Unless the vessel is equipped with two VHF radiotelephones, the VHF radiotelephone shall have dual watch capability if it was installed after April 28, 1996.
A VHF radiotelephone on a vessel shall be capable of transmitting and receiving communications on:
The distress and safety frequency of 156.8 MHZ (channel 16);
The primary inter-ship safety communication frequency of 156.3 MHZ (channel 6);
The bridge-to-bridge communication frequency of 156.65 MHZ (channel 13);
The public correspondence frequency specifically assigned for the area in which the ship is navigating; and
Any other VHF frequencies that is necessary for safety purposes in the area in which the ship is navigating.
A vessel other than a closed construction vessel that does not carry more than six passengers may carry a portable VHF radiotelephone provided that it has a source of energy sufficient for the duration of the voyage.