The idea that a regulator can pre-run the economic actors to price in all known and unknown negative externalities before transactions occur is disingenuous. Competitively breeding an evolving species of ever more creative amoral actors seeking to concentrate benefits and externalize negatives and then somehow hoping you can contain them is madness. In an environment were the 'guards' can and frequently do swap places with the inmates it is beyond madness.

Furthermore, even if that were true there is nothing to stop a malevolent actor, either deliberate, by ignorance, or by lack of better alternatives, to just eat the cost.