The short answer to your question is yes. You're referring to the difference between self-regulation and government-led regulation. Regulations or legislation establishing a framework or requiring compliance ensure that all parties are represented. As you so clearly stated, to date, so far, Loblaw and Walmart have indicated that they wouldn't sign on to a Canadian grocery code of conduct. So there's an inherent problem with the approach.
On April 18th, 2024. See this statement in context.