I would think you would want, on a recurring basis, to make sure that such an inventory was done, so that you would know the extent of the problem. That would help you budget for the removal of the vessels and it would also assess the legal and environmental liability that the vessels pose.
It could be done through regulation. There ought to be a commitment by government to have such an inventory done. I wouldn't necessarily see that it would have to be a part of the law, but it ought to be part of the regulation, I would think.