If Shotgun lovers post on Proof in Belgium re. bbls. weighing <3% of the weight @ original proof being out of proof is correct, that proof law would make good sense & protect the buyer from most (but not all) internal & external bbl. modifications & or repairs.

If nothing else, a step in the right direction.

I've never paid a lot of attention to proof laws other than English so there may be much better proof laws out there to protect the consumer from unscrupulous sellers.

It does seem to me that requiring a minimum wall thickness would be desirable & alterations to forcing cones or chamber length should require reproof as the English proof law does.