I believe the current treaties do allow for extracting resources, but as you say, you can't stake claims. What this means, as far as I understand it, is that if

I believe the current treaties do allow for extracting resources, but as you say, you can't stake claims. What this means, as far as I understand it, is that if you take a resource it's yours but once you leave the extraction site such as an asteroid, someone else can come along and take what's left. You can't claim it's yours because you visited it. I think this is a reasonable approach and I doubt it would be much of a problem in practice. While you are physically present or have assets in place anyone else interfering with you would be infringing on your property - equipment, personnel, etc. That should be enough to establish functioning regulations, although there will be a lot fo details to work out.