It's a sophisticated little problem of criminal law when part of a criminal offence looks like it's taking place in Canada, and another part looks like it might be taking place in another country.
The scenario you're describing involves someone in Canada who's paying for promotional material and advertising, but what they're advertising is for an activity that's going to take place in another country where it may be perfectly legal, so there's a combination of sort of domestic and foreign things happening.
There isn't necessarily a perfectly clear criminal answer on that, except I do feel quite confident in saying that the likelihood of there being a prosecution is incredibly low for something like that.