> I mean, let's say we forbid them from using high S diesel. What happens to this diesel then?

It gets the sulfur refined out of it. It's not hard to do, just not quite as cheap as just burning it somewhere where no environmental regulations exists (or where they are not enforceable).

Elemental sulfur isn't all that nasty, it would be fine in a pile somewhere. The issue is dispersing it into ecosystems quickly. Kind of like fixed nitrogen, which like sulfur is a nutrient

You can see the great stacked blocks of it in Canada where it is removed from the tar sands oil… https://www.google.com/mymaps/viewer?mid=1Wi4KuLBYcXHH0dq4j4...

The oil is more valuable without the sulfur, but the market price of sulfur is low, so they just stack it up.

Don't most laws work like this:

"As of Date X, Y will be illegal." So refiners basically stop making high Sulphur diesel, but date X is far enough in the future that there's time to use it all up before the law takes effect.

Electric cars give away fuel that ships can now use. Of course there’s nowhere to put fuel which shops used to use