I do remember hearing about not wearing sponsored merchandise in interviews and only wearing Maple Leafs items only.
Yeah, that can be enforced. They don't want players looking like Nascar drivers decked out in Red Bull and such. I'd rather they allow it, as it would get the players money, and you'd make more in Toronto doing that then anywhere else as a hockey player.
But, you can't enforce this stuff off the ice. It is a CBA issue that Lou has no control over.
As for Tavares, doesn't he have a Tim Hortons ad? I'm sure brands would line up to sponsor him if he came here. The one thing that slightly hurts Matthews is that he has limited national appeal, and certain companies love the patriotic ads with Hockey Canada association. Although, considering the Leafs probably account for around 1/3 of Canadian hockey fans, and most care more about the Leafs than the Canadian National team, he has a boatload of opportunities.
Tavares as a WJC star, and winning international events would be a marketers dream here. The big knock is, he's a pretty dry personality. Matthews gives pretty standard answers but is pretty personable. Having known people who knew Tavares in London, he isn't really. Its why Wendel makes a killing on the charity golf and paid appearance market these days.