Are there places around the world that offer tours along the old smuggler's trails. US-Mexico or US-Canada would be best but I am open to suggestions.
Smugglers used to have trails across the Swiss/French border in the alps. I just checked, and indeed there is someone offering a tour:
On the web, the tour organizer writes: We will explain how smugglers and customs officials played a cat and mouse game during many years, and how France and Switzerland once went to battle in these very hills and 120 lives were lost.
Also, as far as I know, there have been ancient smuggler's paths in the alps in the vicinity of the border crossing at Saint-Gingolph, Lake Geneva. I am not talking about the WW2 smuggling activities mentioned in the Wikipedia article about that town.