I'm glad you brought me back on that topic because I just went to verify what I had looked up a few years ago on the net, and it looks like the laws concerning the use of metal detectors for treasure hunting are a bit more vague than I previously thought ( in France at least... laws probably vary quite a lot from country to country).
They'll definitely have to stay offline for the time being. But I'll look more into that, as I'd love to be able to share these treasures with you.
And remember: "X never, ever marks the spot" ;)