Or the polluting company with deep pockets would just buy the land and do whatever they wanted.

An unregulated free market is a terrible idea. It ends in massive monopolies and natural resource destruction at an absolute level.

It's not a bad thing that that's what a free market moves towards, per se, but that's why it needs to be and is regulated. Any worthwhile conversation isn't about whether or not to regulate it, it's a what level.

Or you sell the right to abuse the land or waterways. Then turn around and when all the clean water is gone, purify it and sell it!

Carbon rights?

Doesn't sound very appealing for next quarters profits, the true driver of all decisions.