So, back to Domestic and Transborder flights.
Your bag SHOULD NOT BE TAGGED.
If the Customer Service Agent (CSA) insists that it does, then POLITELY refer to the attached PDF below.
Simply (AND POLITELY) ask them to consult the "General Reference Manual (GR) - Airports" for clarification on tagging.
In fact, feel free to hand them the PDF sheet so that they can follow the menu items to get to the correct policy on SSR Codes and WEAP tagging. If the CSA doesn't comply then POLITELY escalate the issue to their station manager. If they still refuse to let you continue without the tag, then feel free to ask for their names or employee numbers and inform them that you will file an email complaint to the email address for Charles Clarke at the bottom of the PDF.
Bear in mind: there are thousands of CSA across a complex network and some are contracted workers, while others are full time WJ employees. It is difficult and challenging to maintain a training standard on an issue that the CSAs do not see every day. So, BE POLITE, give them some space, check-in early to allow yourselves plenty of time to deal with tagging issues, and calmly and POLITELY press the issue on not accepting the bag tag.
One last thing: Did I mention BE POLITE? If I didn't then BE POLITE.
Remember - the company reserves the right to refuse boarding you on the flight if you're a #### (whether you like it or not, or whether you agree with it or not is moot). WestJet will simply refund you your ticket price and point out the location of other airline brands' check-in counters on the departures concourse.