‘(La) Douane’ is the French word for customs, pronounced ‘dwan’ if all those consecutive vowels are confusing you. You may be surprised to hear that ‘douane’ actually has a place in the Oxford Dictionary of English, described as a “custom house in France or other Mediterranean countries”.
What are the roles of the French customs authorities?
Customs officers regulate trade in goods by supervising commercial transactions and indirect taxes (alcohol, tobacco, oil products), and by surveillance of France’s territory and border crossings, performed by uniformed officers.