From Graham Robb’s delightful book The Discovery of France: A Historical Geography, I give you a sample of pp. 151-152:
With an entirely law-abiding population, much of France would have been cut off from the outside world. Smuggling, too, was a major industry that kept the tiny channels of communication open. In some parts, it was practically the only industry. The inhabitants of frontier towns such as Le Pont-de-Beauvoisin, which straddles the France-Savoy border, did little else. Some Provençal villages abandoned agriculture for contraband, and some monasteries had suspiciously large stores of alcohol and tobacco. Nice, which was a separate state until 1860, could export east into Italy and west across the river Var into France.
The frontier between France and Spain was like a sieve. In the west, the hills of the Basque Country were criss-crossed by the smugglers’ paths that were later used by guerrillas, Résistants and Basque terrorists. In the east, Catalans and Roussillonnais ran a thriving criminal economy. A report to the Ministry of Foreign Affairs in 1773 complained that ‘you can’t put one foot in front of the other without running into a band of armed smugglers’. These were not furtive figures creeping about in the undergrowth. They moved in platoons of fifty, with another platoon behind to provide backup. They were fed, paid a salary and divided into ranks like soldiers.
In Brittany, thousands of heavily laden women carrying cakes of salt and over-salted butter poured into Maine, pretending to be pregnant. More than twelve thousand children were tried for smuggling at the salt court in Laval in 1773. This figure included only children who were caught with contraband weighing fifteen pounds or more. When they grew up, some of them would join what was practically an Anglo-French common market. Breton sailors carried brandy to Plymouth while Cornishmen brought tobacco to Roscoff. The sea lanes used by Gallo-Roman traders and Norman invaders remained as busy as ever, especially when Napoleon imposed the Continental System (1806-1813). A smugglers’ slang is said to have been in use on both sides of the Channel. Smugglers from Saint-Malo and Granville could converse with Channel Islanders in Norman French. An American visitor to northern France in 1807 found suspicious signs that, despite Napoleon, Calais and Boulogne were still on excellent trading terms with Dover and Hastings:
Eggs, bacon, poultry, and vegetables, seemed in great plenty, and, as I understood, composed the dinners of the peasantry twice a week at least. I was surprised at this evident abundance in a class in which I should not have expected it. Something of it, I fear, must be imputed to the extraordinary profits of the smuggling which is carried on along the coast.
All this suggests that, while customs barriers stifled trade, they did not necessary increase isolation. The ‘fortress’ of France was remarkably porous. Any commemoration of European unity should remember the smugglers and pedlars who helped to keep the borders open.
Twelve thousand children being tried in any court in a year sounds a little high, but you get the gist.