Of course there is still a lot of digging going on in Belgium and the north of France, I dont think it will ever stop there, its unbelievable howmuch stuff is still outthere, but there is a chance to get nicked of course.
I know for fact that being a foreigner in France doesn't help. Sometimes I see cars with British registration parked, and people walking around with detectors on the battlefields overhere that are part of a museum, a protected national park with graves.
The Gendarmerie also knows this is happening, and thet have a special squad to arrest these diggers. I have met one of them, he is a militaria collector himself and hates foreigners with detectors. If you are lucky you will only loose your detector, if you meet them on a bad day you will get the 5000 euro fine for trying to steel relics and export them. If they find relics in the boot of the car they can take your car and detector, because the car is used to commit the crime. If they find explosives or detonators or anything that even looks dangerous to them in the car, and your car is in the right spot to do so, they can have the bombsquad blow up your car! This sounds unbelievable, but really they have done it before near Arras. If you are being smart by saying you do not understand them or dont speak any French this is also not a problem; they will call for an interpertor and you will have to pay for it at the spot. All costs they have made, even to blow up your car you will have to pay on the spot.
Last but not least; if you get caught with human remains, and believe it or not this has happend before when some guys thought they could simply dig out some graves, you will simply go to prison for a while. I know for fact these guys got a 5 year sentence.
Last year they caught two German "collectors" who where steeling gravestones and selling them as relics on the net. They got a 2 year sentence. I cant say I feel sorry for these lads.