Translate the following English sentence to French:
"The fact is, establishing a single market without internal borders, without these safety valves which, in the final analysis, would not disturb the ordinary citizen, offers an area which is a sheer delight, and a profitable one at that, for criminals of every kind."
En effet, lorsque l' on met en place un marché unique sans frontières intérieures, sans ces clapets de sécurité qui, finalement, ne dérangeraient pas le citoyen ordinaire, l' espace devient un délice, rentable de surcroît, pour criminels en tout genre.