What is the restriction identified on a Canadian Commercial License for a Canadian driver when they are not permitted to operate in the United States for medical reasons?

Some of the Canadian Provinces or Territories have implemented this restriction with a code W on the Commercial License.  Please refer to the 2016 Canadian Driver’s License Reference Guide (PDF) to identify which Provinces or Territories have implemented the code W restriction.  The remaining Provinces or Territories that have not yet implement the code W restriction, have an internal implementation schedule and are working towards adding the code W restriction in their driver licensing systems.