That there are encounters with the law enforcement/Customs during smuggling activities may be crystal clear. Although in Europe the borders are not always visible, it doesn't mean they don't exist.

When smugglers came in contact with the law a cat-and-mouse game happened, sometimes even on life and death, to stay out of hand of the customsofficers "commiezen " (lingo/dialect) (Dutch pronunciation ) as they where called over here.

The locals knew often how to sneak through the border when transporting small amounts.
Smuggling larger of heavier transports where done by specialy prepared motorcycles, cars or lorries That could create oiltracks or could drop caltrops on the road to punch te trires and  to shake off the persuers or to create a save distance so that the smugglers could find a safe haven.

Notice this: In the "early days" (previous to to closing down the bordercontrole in Europe/beNeLux) the border realy was "the border" for law enforcement/Customs etc.
It was absolutly forbidden to cross the border as law enforcement or Customs etc. with a Policeweapon (read: pistol). That was a serious violation of the international agreements.