From what I can gather, the old code framework has been in place...

From what I can gather, the old code framework has been in place for decades and has been relied on by explorers/developers and a succession of Chilean Governments to administer and approve tenements/mining leases, environmental authorities, production / export quotas, exploration and production and much more.

For a Government to consider placing an entirely new interpretation on that legal framework and then apply it retrospectively is almost unheard of.