Oh, I have no doubt the local gendarmerie would arrest you. But if they had no ther probable cause prior to being stopped at the roadblock and they are checking for licenses and not DUI, then they can arrest you, and you can sue their pants off in Fed. Court for civil rights violations.
Fishing expeditions are illegal, and the Fed courts have consistently ruled that the roadblocks are legal only if they are directed towards one problem and not everything.