I suggest you review Rule 75 - Refusal to Transport of the relevant (domestic or international)Tariffs for AC. You'll see that AC has given them quite a lot of leeway with what they can do. However, in order to apply any ban, that decision must be communicated to you.
In addition, from the tariffs, a decision to refuse transport applies to the offending passenger, and it doesn't mention any other passengers travelling with that person.
https://www.aircanada.com/ca/en/aco/...e-tariffs.html