Our jurisdiction is domestic only, but we work very closely with all the national Olympic committees and we do work closely with the USOC when it's relevant. In the instance that you cite, a person could travel into Canada with an infringing T-shirt, assuming they made it into Canada. If it's not shipping in goods, then that's one case.
One thing to be aware of is that, like most sporting events, spectators are subject to the terms and conditions on the backs of their tickets. If there were an instance when thousands were wearing certain marks and therefore creating an ambush platform, that could be addressed through spectator services.